Full-scale model test on prevention of frost heave of L-type retaining wall

    Full-scale model test on prevention of frost heave of L-type retaining wall Dahu RUI PII: DOI: Reference:

S0165-232X(16)30135-5 doi: 10.1016/j.coldregions.2016.07.010 COLTEC 2298

To appear in:

Cold Regions Science and Technology

Received date: Revised date: Accepted date:

30 July 2015 9 June 2016 29 July 2016

Please cite this article as: RUI, Dahu, Full-scale model test on prevention of frost heave of L-type retaining wall, Cold Regions Science and Technology (2016), doi: 10.1016/j.coldregions.2016.07.010

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Full-scale model test on prevention of frost heave of L-type retaining wall Dahu RUI School of Civil Eng., Henan Polytechnic Univ., Jiaozuo, Henan 454000, China

T

Abstract In order to investigate protection against the frost heaving of seasonal frozen soil behind precast L-type

IP

retaining walls in cold regions, test walls were installed in the campus of Kitami Institute of Technology(KIT, Hokkaido, Japan) in two sections (one incorporated countermeasures against frost heave and the other had no

SC R

such countermeasures). The freezing front distribution and ground temperature within the backfill were observed and deflections of the walls were measured over three freeze-thaw seasons. Some understanding of the mechanisms of frost-heave damage was gained. Simulation was undertaken to predict the shape of the freezing front in the backfill behind the L-type walls with various cross sections. These findings were employed to propose a

NU

method for cold regions to determine the appropriate zone for replacement with backfill material not susceptible to frost. For the purpose of improving the utilization of waste recycling, a two-year field test was conducted. In this test, bags filled with granular waste (glass cullet and EPS(expanded poly-styrene )volume reductions) were used as the backfill material of retaining walls in cold regions. This experiment verified that granular waste is suitable for

MA

use as a frost-heave prevention replacement material. This research results have a certain significant in designing the retaining wall of cold regions, waste recycling and protecting the natural environment.

D

Key Words: L-type retaining wall; prevention of frost heave; replacement method; industrial waste recycling;

TE

1. Introduction

In cold regions, freezing of the ground causes a variety of damage to structures in contact with it, such as cracking of paved road surfaces and the frost heave of buildings. Previous studies on frost damage in civil engineering structures

CE P

have mainly addressed countermeasures against frost heave in road subgrades or base courses (Otto, 1981; Tong and Shen, 1982; Wang et al., 2015; Lai et al., 2012). Few have taken such measures for retaining walls, canal works, box culverts or other structures. Generally, construction standards have provided inadequate guidance against frost heave. The fundamentals of frost-heave proofing structures consist of countermeasures against low temperatures, water, or

AC

with regard to soil, but actual construction procedures vary widely (Suzuki et al., 1991; Suzuki and Sawada, 1991; Suzuki and Sawada, 1994). The most trusted and widely employed procedure is to replace the soil within the zone vulnerable to freezing with a material that is not susceptible to frost heave, generally sand or gravel. Thus, the designer must determine the replacement zone and the material that is not susceptible to frost to be used as the backfill (Liu et al., 1994; Uno and Suzuki, 2002; Suzuki et al., 2000). The present study focuses on precast L-type concrete retaining walls of 1m to 4m in height, with the goal of establishing efficient design procedures for a replacement method. Concrete L-type walls were installed in a test bed at Kitami Institute of Technology and freezing conditions, wall deformation and other parameters were observed through the winters over a period of three years (October 1999 to July 2002, the first three years of the test) in order to obtain a precise record of the behaviour of the wall (Rui et al., 2004; Rui et al., 2006; Rui et al., 2007). This test also compared assessed different backfills (replacement materials) and the effectiveness of the replacement method. Computer simulation was undertaken to extend these results to typical conditions by varying the wall configurations and freezing fronts, and to develop a method for specifying the replacement zone. With environmental and resource problems becoming prominent in recent years, the utilization of solid waste embodies further development in the building engineering field (Shoji et al., 1999; Yokota et al., 2002; Olufikayo et al.,2009; Aditya et al.,2013; Franco et al., 2014; Harianto et al., 2013; Alaa M., 2014). The article studies whether or not the particular granular waste is suitable for use as the replacement material for frost prevention. Soil bags filled 1

ACCEPTED MANUSCRIPT with granular waste, consisting of glass cullet and expanded poly-styrene (EPS) to facilitate reduced volumes, were used as the backfill material of the retaining wall. Frost-heave tests on the L-type retaining wall were employed from November 2002 to April 2004(a further two years based on the first three years(1999 to 2002)). The freezing front, ground temperature and the deformation of the retaining wall were observed over the process of freezing and thawing. The granular waste can satisfy the performance requirements of the frost-heave prevention replacement material as

T

empirically tested. Although granular waste is not a susceptible material, the different shapes and the filling method of the backfill may cause deformation of the retaining wall. A method of demolishing the deformed retaining wall and

IP

setting up a new retaining wall is used to explain the reason for the deformation; the frost-heave prevention effects of

SC R

the granular waste are explicit.

2. The frost-heave test of the L-type retaining wall 2.1 Performance of the retaining walls

Figs. 1 and 2 show a schematic representation of the concrete L-type retaining walls, while Fig. 3 shows these in

NU

cross section. The walls are 1.5m high, 2.0m wide and the base length is 1.7m. Nine walls were erected. The overall installation was divided into three sections as described below, each differing with respect to the fill conditions behind each wall.

MA

Slope

D

475 475 200

Immovable point

Frost depth meter

Expanded poly-styrene (width=100)

1:1.5

1:1.5

Measurement point of deflection

TE

(1999.10 - 2002.7) (1999.10 - 2002.7) Volcanic ash soil section (Replacement method) Insulation material section(Insulation method) (2002.10 - 2004.7) (2002.10 - 2004.7) EPS Volume reduction section Glass cullet material section 2000@3=6000 2000@3=6000

(1999.10 - 2004.7) Clayey soil section (No countermeasure) 2000@3=6000

CE P

Fig. 1 Schematic diagram of the retaining walls

AC

(The tests were divided into two parts: the first from October 1999 to July 2002, and the second from November 2002 to April 2004.)

Fig. 2 Photo of test walls in the winter season

2

ACCEPTED MANUSCRIPT

: Thermocouple sensors

1:1 .5

Back- fill zone

1:1 .5

: Inclinometer 100

100

420

1500

420

T IP

420 1500

420

Frost depth meter

200

Inclinometer

200

Calyey soil or Volcanis-ash soil

100

Concrete slab Gravel foundation

Concrete slab

Gravel foundation

NU

1900

（a）Calyey soil or Volcanis-ash soil section

100

400

400

100

200 100 100

200 100 100

100

SC R

Expended poly-styrene (Width=100mm)

1900

(b) Insulation material section

MA

Fig. 3 Cross section of the retaining walls

(1) Volcanic-ash soil section: The “refilled zone” is filled with volcanic-ash soil which is not susceptible to frost. (2) Insulation section: With countermeasures against frost heave, this method uses 10cm thick permeable EPS insulating boarding to prevent the frost penetrating from the wall face.

D

(3) Clayey soil section: The “un-replaced zone” is filled with clayey soil that was prone to frost heave.

TE

Table 1 shows the properties of the backfill material. The volcanic-ash soil is employed in the Hokkaido region for

CE P

roadways as a layer not susceptible to frost. Conversely, the clayey soil is strongly prone to frost heave. Table 1 Soil properties

AC

Soil type

ρs (g/cm3) Gravel (%) Sand (%) Silt (%) Particle size distribution Clay (%) Cu Cc wopt (%) Compaction ρdmax (g/cm3) Frost-heave Frost-heave test ratio (%)

Clayey soil （backfill) 2.59 5.80 57.0 27.5 9.70 43.4 1.74 29.3 1.31

Volcanicash soil 2.50 13.9 63.9 18.2 4.0 21.2 1.37 25.5 1.13

Clayey soil (flat field) 2.51 1.8 45.9 39.3 13.0 27.9 0.56 26.0 1.39

0.71

0.01

0.48

The inclinometers and copper-constant thermocouples were installed as shown in Fig. 3 to measure the action of the walls and the temperatures of the front and back surfaces of the wall. The inclinometer and thermocouple sensor readings were automatically recorded every 2h. The rated capacity of the inclinometer is ±5º. The operating temperature range of the inclinometer is -20～70℃. The frost depth in the backfill was also measured once a day with a methylene-blue frost-depth meter and recorded. Meanwhile, in order to master the freezing condition of the soil during the experiment, the ground temperature, frost depth, frost-heave amount and frost-heave force were measured in the flat field test (Fig.4). The distance from the flat field test filled with clayey soil to the retaining wall is 100m. Table 2 shows the properties of the clayey soil (Suzuki et al., 1995).

3

ACCEPTED MANUSCRIPT Reaction frame Load cell Iron disk

(frost heave force)

(frost heave amount) Spacer

SC R

Methylene blue forst depth meter

IP

T

Anchor rod ( 40

1200

100

Concrete anchor

Fig.4 Flat field test installation

NU

2.2 Results and discussions (1) Ground freezing conditions

The mean daily temperature, frost-heave amount, frost depth and frost-heave force of three seasons from November 1999 to April 2002 in the flat test field are shown in Fig. 5, respectively. The freezing index in the first season is

MA

875℃·days, second season 1077℃·days and third season 737℃·days. Considering the tendency for warm winters in recent years, the three experimental seasons had a comparatively strong tendency for cold. The second season especially shows the highest freezing index of the past ten years. The frost-heave pressure is the force acting on a disk with a diameter of 10cm on the ground’s surface.

D

Fig.6 shows the max frost depth, max frost-heave amount and max frost-heave force relationship with freezing index.

TE

The variation range of the max frost depth, max surface frost-heave amount and max frost-heave force are within 67.5～90.2cm, 6.1～11.8cm and 56.5～85.5kN, respectively. But the correlation between max frost depth, max frostheave amount and freezing index is not explicit. Temperature gradient, the main thermal physical parameters for

CE P

controlling the frost-heave amount, is not closely related with the freezing index that represents the degree of cold weather. Although the max frost depth is strongly influenced by freezing index, the occurrence of ground frost-heave also impact the development of frost depth. The frost-heave occurred along the ground freezing in middle December

AC

and began to reduce gradually to zero in late March.

Fig. 6 Max frost depth, max frost-heave amount, max frost-heave force of the experiment season

4

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Fig. 5 Ground freezing conditions of the experiment season

AC

Heat flow

¦Ò y

Freezing front

¦Ò n ¦Ò x

(c) Enlarged ice lens trace Heat flow

¦ nÒ:Normal frost heave force ¦ xÒ:Horizontal component ¦ yÒ:Vertical component (a) Cross section backfill soil

Fig. 7 Frost penetration of backfill

(b) Concrete crack

Fig. 8 Typical crack of the L-type retaining walls

5

ACCEPTED MANUSCRIPT (2) Frost penetration of backfill Fig. 7 shows the mode picture of frost penetration of backfill and Fig. 8 shows the cross-section of the backfill soil where frost-heave occurs . Generally, the frozen front is parallel to the plane exposed to the atmosphere and vertically invade the wall surface. The upper heat flow of vertical wall is greater than the lower, so the frozen surface behind the wall is not possibly parallel to the vertical wall. When the air temperature below the freezing temperature, pore water generated crystal, ice crystal formed and

T

increased constantly. In the process of the soil particle spacing extended to the soil particle displacement, the formation

IP

of different thickness ice lens is induced by the outside water flow invasion. When the freezing front can not get the water supplement and the thermal equilibrium state was destroyed, the freezing front moved downward and arrived the

SC R

next equilibrium, then the new ice crystal formed. Thus, the law of the stratified distribution of ice crystal in frozen soils was formed during the freezing process. After the three freezing and thawing cycles, the soil cracks (the trace of freezing surface) induced by the ice crystal could be seen clearly in Fig. 8.

The frost-heave pressure acts on the normal direction of the freezing front or the direction of the heat flow (Phukan, 1985). Therefore, if the shape of the freezing front can be established, the designer can calculate the size of the fill zone

NU

behind the wall where frost-heave damage occurs and tends to deform the wall. Understanding the shape of the freezing front in the backfill is the primary task and one of the most essential countermeasure tasks for protecting civil engineering structures against frost-heave damage. following can be inferred from these figures:

MA

Fig. 9 shows the shapes of the backfill freezing front deduced from the methylene-blue frost-depth meter data. The (1) The shape of the freezing front is primarily influenced by surface topography (the heat outflow surface). The frost-heave force acts normal to the freezing front. A steep freezing front is associated with the flow of heat out of the

D

volcanic-ash soil zone or clayey soil zone through the wall. When the freezing front has this shape and there is frost

TE

heave in the backfill, it increases the horizontal frost-heave force tending to push out the front face of the retaining wall. (2) The heat flux of the retaining wall is blocked by the EPS insulating material, leading to the shape penetration of the freezing front slightly tending to parallel with the surface topography, but there is no parallel. As a result, it is

CE P

impossible that the horizontal component of the frost-heave force is equal to zero. (3) Comparison of the results within the backfill zones indicates that freezing penetrated to a greater depth in the second season (2000-2001). This is consistent with the freezing index, an indicator of the coldness of the winter, which was the greatest during the second winter. Comparing within the seasons, the volcanic-ash soil section shows penetration of the frozen zone to a greater depth than the clayey soil section. Discrepancies in frost depth are attributed

AC

to discrepancies in water content; generally, because of the higher latent heat of freezing the greater the water content, the more shallow the frost depth.

6

Snow

120 0

40

80

120

160

40

80

120

160

T 1 Dec

80

120

160

120

160

Sn ow

120 80

NU

Freezing front

2000-2001

0

0

1999-2000

40

1 Jan 1 Feb 1 Mar

160

160 120

1 Mar

40

40

Freezing front

200

Sn ow

1 Feb

80

80

120

160

1 Jan 1 Feb 1 Mar

1 Dec 1 Jan

0

SC R

200

200

Sn ow

IP

160

0

40

80

120

40

120

Freezing front

2001-2002

0

80

0

0

2001-2002

(a) Volcanic-ash soil section

1 Dec

Freezing front

40

40

Freezing front 2000-2001

0

40

Snow

80

80

80 40

Freezing front

0

1 Jan 1 Feb 1 Mar

1 Mar

1999-2000

0

200

1 Feb

1 Dec

160

200 160

Snow

1 Dec 1 Jan

120

200

1 Jan 1 Feb 1 Mar

120

1 Dec

160

ACCEPTED MANUSCRIPT

160

0

40

80

Snow

200 Snow

1 Dec 1 Jan 1 Feb 1 Mar

160

MA 200

1 Jan 1 Feb 1 Mar

Unit: cm

1 Dec 1 Jan 1 Feb

160

200

1 Dec

160

(b) Insulation material section

Snow

120

120

40

80

120

160

CE P

0

80

80

40

40

2000-2001

2001-2002

0

0

1999-2000

Freezing front

Freezing front

0

40

Freezing front

TE

80

D

120

1 Mar

0

40

80

120

160

0

40

80

120

160

(c) Clayey soil section

Fig. 9 Freezing-front shape of the backfill earth

(3) Behavior of retaining walls Fig. 10(a) is a graph showing the time-dependent change in the inclination of each wall. In the clayey soil section,

AC

where no particular frost-heave prevention is employed, the wall begins to tilt almost simultaneously with the onset of freezing in every season. The maximum values of this inclination are 3.7º, 5.4º and 6.3º in the first, second and third seasons, respectively. The maximum deflection of the top of the wall after the beginning of the experiment is approximately 14cm in the third season. The inclination of the vertical wall rebounds partially after the back fill begins to thaw in late March, but some tilt remains after complete thaw in summer and tilting of the wall is observed to be cumulative. It is apparent that tilting of the vertical wall supporting the clayey soil backfill is due to frost-heave pressure. The tilt and the displacement of the top of the wall clearly exceed the allowable values for concrete, and cracks occurred at the foot of the wall (Fig. 8). This is typical for frost-heave pressure-induced cracking in concrete L-type retaining walls. In the insulation section, the maximum values of the inclination are 2.2º, 2.5º and 2.6º in the first, second and third seasons, respectively. Compared with the clayey soil section, where no particular frost-heave prevention is employed, the deformation reduced by half. This illustrates the effectiveness of the thermal insulation measurement, but as a countermeasure against frost heave, it is still insufficient. It can be seen from the distribution of the freezing front shape that the horizontal component of the frost-heave force is not equal to zero. Almost no tilting of the vertical wall was observed in the volcanic-ash soil section throughout the observation periods. A conspicuous advantage is gained by replacing the soil with the volcanic-ash soil backfill which is not susceptible to frost within the zone most vulnerable to frost damage. No cracking like that shown in Fig. 8 was ever observed, even after the three seasons of observations of this section. 7

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Fig. 10 Inclination of wall over three seasons

Fig. 10 (b) shows the progression in inclination of the base of each wall. Slight but detectable tilting occurred in

MA

both sections during the winter seasons. The reason for the absence of further tilting during the third winter is thought to be due to the spreading of the cracks in the lower regions of the vertical walls, which may have reduced transmission of the forces from the vertical walls to their bases. The tilting of the base is markedly less than that of the vertical walls, and the bases returned to the horizontal during the unfrozen seasons. There is almost no

D

tilting (rotation) of the wall monoliths ascribable to inadequate support by the underlying bed. The tilting and cracking

3 Designs of backfill zones

TE

of the vertical walls is attributed entirely to frost-heave pressure.

CE P

3.1 Method for determining backfill zone The previous sections described (i) the results of the observations of the dynamic behavior of L-type concrete retaining walls during the freezing season, (ii) the situation of wall failure during backfill freezing, and (iii) the mechanisms of that failure. Here, procedures for the design of countermeasures against frost heave by replacement are

AC

proposed on the basis of those observations.

A

e



n ¦Ò

C

£ ¡°ãCli ne Border point

d

a

Replacement zone



 :Frost depth

b

c 

£ ¡°ãC l  ine

Fig. 11 Proposed replacement zone

Fig. 11 shows the proposed method for determining the zone to be replaced with backfill material not susceptible to frost. The frost heaving force acts on the normal direction of freezing front or the direction of heat flow, therefore,

it is the frost heave force acting on the vertical wall, which mainly induced by the freezing front of zone(a-b-c-d). 8

ACCEPTED MANUSCRIPT According to the principle, set the part that including the freezing front as the replacement zone. When the frost depth is Zf, the zone throughout which the frost-heave forces can be considered to act upon the rear face of the vertical wall (plane c–d) is the volume extending back to the (a–b) line. Here, point a is referred to as the border point. Thus, it is assumed that replacing the volume represented by the cross section (a–b–c–d–e) is sufficient to prevent push out.

T

Where A ,B are the upper width, the bottom width of the replacement zone, respectively. C is the vertical distance from upper horizontal plane of replacement zone to the border point.

IP

The Japanese standards for retaining walls specify that the penetration depth of L-type retaining walls must extend at least 50cm (Guidance for earth worker, 2012). It was assumed that there was no penetration depth in the calculations of

SC R

the freezing distributions in Fig. 11. The penetration depth varies with site, support offered by the underlying soil and several other conditions, and all should be taken into consideration when designs are too be implemented in critical locations. Fig. 11 also does not consider the influence of drifting snow on the shape of the freezing front. If the heatinsulating effect of drifting snow was considered, the replacement zone could actually be reduced in size, but it is difficult to make any quantitative estimates of this effect. This analysis causes the above assumptions to estimate a

NU

relationship between the maximum frost depth Zf and the parameters A, B and C, in order to determine the replacement zone (a–b–c–d–e) in Fig. 11.

MA

3.2 Numeric simulation Before predicting the extent of the replacement zone in Fig.11, the shape of the freezing front must be approximated; this is attempted using numerical simulation (Uno et al., 2002). Two-dimensional unsteady thermal conduction incorporating the latent heat associated with freeze–thaw is assumed in developing the fundamental equations for the analysis. User-determined parameters are the cross-sectional shape of the analytical model, the thermo-physical

D

properties of the materials（thermal conductivity，volumetric specific heat，volumetric water content） and the

TE

meteorological conditions（atmospheric temperature，wind speeds）. The thermal parameters of all media are

listed in Table. 2.

Table 2 Thermal parameters of the media Soil

Concrete

Frozen soil thermal conductivity (W/m･K)

1.2

2.55

Unfrozen soil thermal conductivity (W/m･K)

1.8

2.55

2500

2510

40

0

CE P

Parameter

3

Volumetric specific heat (J/m ･K)

AC

Volumetric water content (%)

The meteorological data from the weather observation system(AMeDAS) on the KIT campus is employed for the latter parameters and the soil temperature at a depth of 5m is assumed to be constant at 9ºC. The atmospheric temperature data set is from the winter of 2000, which had been the coldest winter in the previous 10 years.

Fig.12 shows the simulation result of the freezing front distribution of the volcanic ash soil section(except the snow section) in 2000. （●）is the actual measured frost depth by the frost depth meter. As shown in figure 12, the shape of the freezing front in numerical simulation approximate the actual measured value, which illustrates the appropriateness of the numerical simulation.

9

SC R

IP

T

ACCEPTED MANUSCRIPT

Fig. 12 Comparison of actual measured value and

Fig. 13 An example of simulation result

NU

numerical simulation value

Fig.13 presents an example of the simulation results(without slope). Soil isotherms are indicated by white lines at intervals of 1ºC. This analysis compared different shapes of the retaining wall rear face (presence vs. absence of slope;

MA

berm width; and wall height) for their effects on the shape of the freezing front. A draft manual for the design and construction of precast L-type retaining walls covers walls of heights from 1m to 4m, so this range is investigated in this simulation. Fig. 13 is an example of the isotherms at an arbitrary time. This group of lines can be considered to be the change in the freezing front over time. This analysis is carried out for several wall surface configurations and the

D

relationship between freezing depth Zf and replacement zone parameters A, B and C are elucidated for each freezing-

TE

front configuration.

3.3 Frost depth Zf Parameters A, B and C, which describe the replacement zone, are determined by the frost depth. Fig. 14 shows the

CE P

relationship between the freezing index and the frost depth. This figure shows the relationship calculated for a onedimensional case under level ground. Maximum dry density ρdmax and optimum water content wopt are also employed as

180 160

H=100cm H=200cm

140

H=300cm H=100cm

120

Regression curve

100







0℃

40



0℃

0℃













 





20





100

110



0 0

10

20

30

40

50

60

70

80

90

120

Frost depth Zf (cm)

Fig. 14 Frost depth and freezing index







60



80



A (cm)

AC

parameters, but these are known to correlate with soil type and thermo-physical properties.

Fig.15 Frost depth and A for differing wall heights

10







ACCEPTED MANUSCRIPT

H=200cm







100



 0℃

















0℃





 











Regression curve

120







80

T

B (cm)

0℃

H=300cm H=400cm



 

 0℃

140



H=100cm





 160



180

60

IP

40 20 0 10

20

30

40

50

60

70

80

90

100

110

120

SC R

0

Frost depth Zf (cm)

Fig. 16 Freezing depth and B for the differing wall heights Fig. 17 Freezing depth and C for differing berm widths

3.4 Determining A, B, C Fig. 15 plots the relationship between A and Zf for different wall heights. The curve predicted for a wall height of

NU

100cm resembles those for the higher walls up to a frost depth of about 40cm. Behind a low, 100cm wall, when Zf is 80cm, the upper face of the step matches the depth of the border point (point a in Fig.11). In this case, if the frost depth is increased further, the calculations shows that A tends to decrease. For the purpose of designing actual structures,

MA

however, A is fixed at a constant 80cm in freezing depths, deeper than 80cm, behind 100cm walls, as shown Fig. 15. Fig. 16 presents the relationship between parameter B and Zf for the four wall heights. There are minor differences between the wall heights because B is determined by the shape of the freezing front at the lowest portion of the wall, which is itself only slightly influenced by wall height or berm width. B is fixed at 80cm for frost depths exceeding

D

80cm behind 100cm walls, for the same reason as A is fixed as described above. Thus, for 100cm walls in locations

TE

where freezing is expected to reach depths of at least 80cm, a comparison of Fig. 15 and Fig. 16 shows that A = B. This means that the soil replacement zone is rectangular in cross section. Fig. 17 depicts the relationship between depth parameter C and Zf for differing berm widths D. The freezing front

CE P

shape is dominated by the topography of the surface, but the narrower the berm, the more closely the freezing front parallels and approaches the vertical wall, so that the border point approaches the top of the wall. Over longer berm widths, conversely, the freezing front in the backfill approaches a wedge shape, due to heat flow out of the ground

surface behind the wall, and the border point recedes from the top of the wall. Similar to the limiting approximations of parameters A (Fig. 15) and B (Fig. 16), C is set to 100cm for the 100cm wall and Zf ≥ 80cm, calling

AC

for a rectangular cross-section backfill.

4. Frost heave experiment of retaining wall backfilled with granular waste 4.1 The properties of granular waste In this study, the particular properties of the material not susceptible to frost and the insulation material are emphasized in the selection of the replacement material, as the EPS volume reduction material and the glass cullet material are employed. The EPS volume reduction material is made from abandoned EPS that had experienced heating–melting and cooling solidification granulation, with the properties of being light weight, good insulation and with weak water absorption. Table 3 shows the physical properties of the material employed in this experiment. The EPS volume reduction material and the glass cullet material are the materials not susceptible to frost. Table 3 Properties of replacement material EPS volume reduction 1.0

Material type ρs (g/cm ) 3

Glass cullet 2.44

Maximum grain size（mm)

9.5

19

Thermo conductivity (W/(m・K))

0.08

0.31

Natural moisture content（%）

0.22

0.04

Frost-heave ratio (%)

0.05

0.03

11

ACCEPTED MANUSCRIPT 1:1 .5

1:1 .5

800 400

800 700

100

1:1 .5

100

IP

 Gravel foundation 1900

SC R

1900

(b) Glass cullet material section

(a) EPS Volume reduction section

100

400

100 200 100100

Gravel foundation

T

400

100



420 1500

200

420

: Inclinometer

Glass cullet material 200 100100

100 200 100100

: Thermocouple sensors

f

c 400

EPS Volume reduction material

Frost depth meter

420

200

e

420

b

d

420 1500

40

300 100

200 420

a

1500

300 100

Back-fill zone Calyey soil

 Gravel foundation 1900

(c) Clayey soil section

Fig. 18 Cross section of the retaining walls

4.2 Performance of retaining walls

Purely in terms of the backfill behind the retaining wall, the soil bags filled with waste material may not make much

NU

sense, but they have the following advantages in the long run: ① they arbitrarily change the shape and are easily constructed; ② the soil bags without any limitation, even the granular waste, do not pollute the foundations and are a good method of waste recycling; ③ increasing the intensity of the granular material reduces the soil pressure of the

MA

retaining wall ; ④ the soil bags restrain the capillary water rising and effectively prevent the frost-heave.(Matsuok and Liu, 2003; Li et al., 2013; Li et al., 2015).

The effectiveness of the replacement method is explained and a method for determining the effective replacement zone is proposed through the frost-heave experiment of the retaining wall over three freeze–thaw seasons (1999–2002).In order

D

to verify the frost-heave prevention effects of the granular waste, as a continuation of the former experiment, the retaining

TE

wall in this test is as shown in Fig. 1. This test set the clayey section, glass cullet section and EPS volumes reduction section. Fig. 18 shows the cross section of the retaining walls (parts of them were changed in 2003). The granular glass cullet and the EPS volume reductions are put into soil bags, according to the size of the position,

CE P

ordinarily behind the retaining wall, with other space filled with the clayey soil that was prone to frost heave and backfill compaction. Fig. 19 shows the construction statues of the backfill. In this paper, the volcanic-ash soil section is considered to include no countermeasures against frost heave, while the glass cullet section and the EPS volume reductions section incorporate countermeasures against frost heave. In the clayey soil section, the retaining wall continues

AC

to use the wall set in 1999.

Fig. 19 Construction of the granular-waste-filled bags

4.3 Results and discussions (1) Ground freezing condition The mean daily temperature, frost-heave amount, frost depth, and frost-heave force of three seasons from November 2002 to April 2004 in the flat test field are shown in Fig. 20, respectively.

12

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

MA

Fig. 20 Ground freezing conditions of experiment season

The freezing index in the first season was 1030℃·days, the second season was 677℃·days. The frost depth reaches the maximum value in the middle of March, at 87.5cm and 69.3cm in the first and second seasons, respectively. Simultaneously, the maximum values of the frost-heave amount were 10cm and 7.2cm in the first and second seasons,

D

respectively.

TE

(2）Frost penetration of backfill

The frost-heaving pressure acts in a normal direction to the freezing front. Therefore, it is very important in the frostheave prevention design that the constructions master the freezing front shape correctly. Fig. 21 shows the temperature

CE P

distribution of the backfill in the glass cullet section and the EPS volume reductions section (the layout of the temperature measuring point is shown in Fig. 18). The upper temperature of the replacement material is largely influenced by the mean air temperature: the temperature changed significantly, and its value is close to the mean air temperature. The temperature of the middle part and the lower part kept steady, changed a little and always positively. Fig. 22 shows the freezing front shape of the backfill calculated using a frost-depth meter and the temperature of the

AC

soil as shown in Fig. 18. The freezing front shape is closely related to the surface topography, and because the heatbudget conditions of the top and lower regions of the retaining wall are different, so the freezing front behind the retaining wall is not parallel to the walls. As shown in Fig. 22, the insulation of the granular material used to fill the soil bags can control the freezing front in the replacement material, which ensures the stability of the retaining wall.

Fig. 21 Temperature inside and outside the replacement material

13

ACCEPTED MANUSCRIPT

1 Feb

1 Feb

1 Mar

160

1 Jan

1 Feb

160

1 Jan

120

1 Mar

120

Freezing front

120

1 Jan

200

1 Mar

1 Dec

200

200 160

1 Dec 1 Dec

Freezing front

80

120

160

T

40

IP

40

40

0

80

120

160

40

0

80

120

SC R

0

2002-2003

0

40

2002-2003

0

0

40

2002-2003

80

80

80

Freezing front

160

Unit: cm

1 Dec 1 Jan

Concrete block

80 120

160

40

0

80

Freezing front

2003-2004

0

MA

80

2003-2004

40 0

40 0

40

(a) Glass cullet material section

120

NU

120

Freezing front

80

160

160 80

120

Freezing front

2003-2004

160

1 Feb 1 Mar

40

1 Feb

0

1 Mar

1 Jan

1 Mar

1 Feb

200

1 Dec

200

200

1 Dec 1 Jan

120

160

0

(b) EPS Volume reduction section

40

80

120

160

(c) Clayey soil section

TE

(3) The deformation of the retaining wall

D

Fig. 22 Freezing-front shape of backfill earth

a) The deformation of the retaining wall without countermeasures against frost heave Fig. 23(a) shows the progression in inclination of the vertical wall and the bases of the clayey soil section, where no

CE P

particular frost-heave prevention occurred. The wall began to tilt almost simultaneously with the onset of freezing in every season in the five years since the walls were set. The maximum values of this inclination are 3.7º, 5.4º and 6.3º in the first, second and third seasons, respectively. The fourth season is 7.2º and the fifth season is 7.8º. As shown in the figure, the inclination of the wall rebounded partially after the backfill began to thaw, but some tilt remained after complete thawing and the tilt was observed to be cumulative until the wall was completely destroyed.

AC

The progression in inclination of the bases changed slightly, as shown in Fig. 23(b); the inclination variation being from +0.1º in the first year to -0.3º in the fifth year. In this paper, (+) indicates the relative subsidence inclination in front of the bases, (-) indicates uplift of the bases . It was not until 2001 that the maximum value of inclination of the bases was (+) during the freezing period, while in the thawing season it was (-), influenced by the horizontal frostheave force of the backfill. The reason the inclination of the bases was (+) is that the rotating moment induced by the horizontal frost-heave force, which acts on the wall, transfers to the wall foot, which causes the inclination change in the bases. From 2002, the inclination of the bases was (-) and accumulated year after year. As a result, with the increase in the cracks in the lower regions of the walls, the horizontal frost-heave force could not transfer to the bases, while frost heave in the foundations caused the bases to rise. b）The deformation of the retaining wall with countermeasures against frost heave Fig. 24 shows the inclination variation of the wall in the glass cullet and EPS volume reductions sections from November 2002 to June 2004. As shown in Fig. 24, the behavior of the retaining walls set in the glass cullet and EPS volume reductions sections in 2002 resembled the clayey soil section, and the walls began to tilt at the same time. In early March, the inclination presented the maximum values of 1.1º in the glass cullet section and 1.4º in the EPS volume reductions section, with deflection of the crown at 3cm and 2.1cm, respectively. After the experiment in 2002, the EPS volume reductions section of the wall was replaced and it was found that there were several horizontal cracks in the wall. The walls of the glass cullet and EPS volume reductions sections 14

ACCEPTED MANUSCRIPT began to tilt simultaneously with the onset of the soil-freezing penetration, and the inclination presented the maximum values in the middle of March. Compared with the volcanic-ash soil section, whose deflection of the crown was 5.0cm, the inclination of the wall rebounded rapidly along with the thaw, evidence that the glass cullet and EPS volume reductions sections achieved remarkable effects. In order to correctly evaluate the frost-heave prevention effects of the

NU

SC R

IP

T

granular material, it is necessary to clarify the reasons for the deflection of the wall.

Fig. 24 Inclination of wall over two seasons

MA

Fig. 23 Inclination of wall over five seasons

Fig. 25 shows the deflection mechanisms of the wall with countermeasures against frost heave. As shown in Fig. 22, the freezing fronts of both sections with countermeasures against frost heave remained in the replacement material at

D

all times, they did not penetrate into the susceptible clayey soil at the back of the replacement material. Therefore, it is

TE

impossible that the frost heave in the granular waste in the soil bags induced the deflection of the wall. Due to the good water permeability of the waste bags, the deflection of the wall could not have been caused by the freezing and expansion of the water left in the waste material. According to the analysis above, deflection of the wall should not

CE P

have happened.

Fig. 25 shows soil 10cm thick with turf on the top of the replacement material behind the wall. Due to the good thermal insulation properties of the replacement material cutting across the heat flux in the lower regions of the wall, the freezing speed of the soil with turf is better than that of the slope soil during the freezing period. Therefore, it may be assumed that the horizontal component σx of the normal frost-heave force σn acts on the slope soil through the g-h-

AC

d-f frozen soil transfer to the top of the wall, which induced the deformation of the wall. Fig. 24 shows the deflection of the wall in both sections where the replacement method recovered rapidly along with the thawing of the backfill. This presents an apparent contrast with the volcanic-ash soil section. As a result, the rapid thawing of the g-h-d-f frozen soil cut across the σx that acted on the wall, inducing the rapid recovery of the wall.

15

ACCEPTED MANUSCRIPT ¦ nÒ ¦ xÒ

Vegetative soil

¦ xÒ

a

g

h d

f

T

Fro sthe ave for ce e

Replacement zone

IP

fro nt

a'

¦ nÒ:Normal frost-heave force ¦ xÒ:Horizontal component ¦ yÒ:Vertical component b

SC R

¦ yÒ

c' c

NU

Fre ez ing

Fig. 26 The setting of the concrete block

MA

Fig. 25 The reason for the inclination of the wall

c) The improvement in and results of the retaining wall The experiment was undertaken in 2003. In order to prevent transmission of the horizontal frost heave σx from the slope soil to the top of the wall, a concrete block that can freely move was set at the top of the wall, as shown in Fig.

D

22(a), (b) and Fig. 26. Fig. 24 shows the inclination variation of the walls in the glass cullet and the EPS volume

TE

reductions sections after the above measures were taken. The wall of the clayey section is the same as in 2002, the walls began to tilt simultaneously with the onset of the freezing soil and deflection reached the maximum value in early March. While both sections incorporated frost-heave countermeasures, nothing happened at any time. After the

CE P

experiment ended in 2002, a new wall replaced the EPS volume reductions section, so the initialization was zero in 2003. In addition, it was found that the concrete-block paving at the top of the wall had slid out by approximately 1.5cm after the thaw of the slope soil was complete, further verifying that the deflection of the wall was caused by the horizontal frost force σx of the slope soil, thus the effectiveness of the granular material used as a frost-heave gravel.

AC

prevention material is explained. Its action effects are the same as the ordinary replacement material, generally sand or The horizontal frost-heave force σx cannot occur if the retaining wall has no slope soil. But with slope soil, the influence of frost-heave force acting on the slope soil must be fully taken into consideration. The wall’s density can adequately resist the soil pressure in design, but unexpected destruction will occur when the backfill is subjected to frost heave.

5. Summary This study combines the results of outdoor experiments with ground freezing at concrete retaining walls installed in the KIT campus with the results of simulations of ground freezing. The study proposes a method for determining the soil replacement zone in order to minimize the deleterious effects associated with freezing. With the propose of improving the utilization of waste recycling, for two years the experiment used bags filled with granular waste (glass cullet and EPS volume reductions) as the frost-heave prevention material of retaining walls in cold regions. The conclusions can be summarized as follows: (1) If the backfill behind a concrete wall is allowed to be subjected to frost heave, accumulation of the deformation of the wall monolith occurs, eventually causing the wall to fail. (2) Beneficial effects were associated with using backfill that was not susceptible to frost behind concrete retaining walls. (3) If the frost depth Zf of the installation site is known, the fill volume parameters A, B, and C can be found using 16

ACCEPTED MANUSCRIPT Fig. 15, Fig. 16 and Fig. 17, respectively, and can be used to determine the soil replacement zone necessary for an effective countermeasure against frost-eave pressure. (4) The effects of the frost-heave prevention measures of the granular waste used in the test are significant. So the granular material could be used as a frost-heave prevention replacement material. Currently, a quantitative assessment of the applicability of replacement material is rather difficult in cold regions. Generally, the qualitative assessment is more. As a frost-heave prevention replacement material, its elementary

T

requirement are the materials not susceptible to frost. It has been confirmed that the two granular material being used

IP

are not susceptible to frost in the laboratory test. But as the backfill material, the requirements of strength, durability or construction management methods and so on are not fully specified. In this experiment, soil bags filled with granular

SC R

material (about 20cm) are paved every two layers. Then the retaining wall is finished by the compaction method of the vibratory plate compactor. And there is no problem in the function of the retaining wall. In this study, empirical methods are not limited to the glass cullet and EPS volume reduction material, such as, molten slag，coal ash，crushed plastic, etc. It is possibly suitable for use as long as the granular materials is not susceptible to frost. Most of the granular materials are used in their initial state or a simple broken material. Comparing

NU

with the sand , gravel and other ground materials explored from the nature, it is economically viable. Therefore, this research results have certain significance in waste recycling and protecting the natural environment.

MA

Acknowledgments The authors acknowledge financial support from the National Natural Science Foundation of China (Grant NO.41371092).This research was partially supported by the Scientific Research Starting Foundation for Returned Overseas Chinese Scholars, Ministry of Education, China, the State Key Laboratory of Frozen Soil Engineering (SKLFSE201402), National Key Scientific and Technological Project of Henan Province Office of Education, China

References

TE

D

(Grant NO.14B170007) and the Doctoral Scientific Fund Project of Henan Polytechnic University (Grant NO.648347).

[1] Aditya Kumar Anupam, Praveen Kumar, G.D. Ransinchung R.N., 2013. Use of various agricultural and industrial waste materials in road construction. Procedia-Social and

CE P

Behavioral Sciences, 104(2), 264–273.

[2] Alaa M. Rashad, 2014. Recycled glass as fine aggregate replacement in cementitious materials based on Portland cement. Construction and Building Materials, 72, 340–357. [3] Bisceglie, F., Gigante, E., Bergonzoni, M., 2014. Utilization of waste autoclaved aerated concrete as lighting material in the structure of a green roof. Construction and Building Materials, 69, 351–361.

[4] Guidance for earth worker & retaining wall worker. Toyo: Japanese Road Association, 2012. (in Japanese) [5] Harianto Rahardjo, Alfrendo Satyanaga, Eng-Choon Leong, Jing-Yuan Wang, 2013. Unsaturated properties of recycled concrete aggregate and reclaimed asphalt pavement.

AC

Engineering Geology, 161, 44–54.

[6] Liu, C-G., Suzuki, T., Sawada S., Onaka,T.,1994. Field tests on protection methods against frost actions using gravel and permeable thermal insulating material, Journal of Geotechnical Engineering, JSCE, 487(3–15), 265–270. [7] Matsuok, A.H., Liu, S.H., 2003. New earth reinforcement method by soil bags. Soil and Foundations, 43(6), 173–188. [8] Otto J. Svec, 1981. Frost heave control of a chilled gas pipeline. Cold Regions Science and Technology, 4(3), 215–225. [9] Olufikayo Aderinlewo, Nii-Attoh Okine, 2009. Sensitivity analysis of a scrap tire embankment using Bayesian influence diagrams Construction and Building Materials, 23(3), 1446–1455. [10] Phukan, A., 1985. Frozen ground engineering. Englewood Cliffs, N J: Prentice Hall Inc, 139–169. [11] Rui, D.H., Suzuki, T., Yamashita, S., Hyashi, K., 2004. Study on countermeasure to frost heave of precast L-type retaining walls. Journal of Geotechnical Engineering for JSCE, 771(3–68), 215–224. (In Japanese) [12] Rui, D.H., Suzuki, T., Yamashita, S., Hyashi, K., 2006. Countermeasure for frost heave of concrete L-type retaining wall backfill with granular wastes. Journal of Geotechnical Engineering for JSCE, 62(3), 562一572. (In Japanese) [13] Rui, D.H., Suzuki,T., Kim, Y.S., 2007. Frost heave force of natural ground countermeasure for damage of structures. Journal of the Korean Geotechnical Society, 23(5), 43一 51. (In Korean) [14] Suzuki, T., Ueno, K., Hayashi, K., 1991. Preventing measure of frost heaving damage on small sized U-trough using gravel backfill. Journal of Geotechnical Engineering, JSCE, 439(III-17), 89一96. (In Japanese) [15] Suzuki T., Sawada, Onaka, 1991. Field tests on frost heaving characteristics of ground. Journal of Geotechnical Engineering, JSCE, 430(3–15), 107–114. [16] Suzuki, T., Sawada, S., 1994. Full-scale model test on frost heaving pressure in a reinforce retaining wall. Proc 7th INT Symp 316.on Ground Freezing, A. A. Balkema 311– 316. [17] Suzuki, T, Uno, H., Sawada, S., Adachi, K., 2000. Freezing front and frost heaving pressure in multi anchored retaining. Journal of Geotechnical Engineering, JSCE, 645 (3–50), 281–290. (In Japanese) [18] Shoji, Y., Takahashi, K., Asai, T., Kadano, T., 1999. Utilization of fly-ash cement mixture for backfills of quay. The Japanese Society of Civil Engineers, 637(6–45), 137–148.

17

ACCEPTED MANUSCRIPT [19] Suzuki, T. Qing Zhu, Sawada, S., 1995. Experimental study on frost heaving force of natural ground. Journal of Geotechnical Engineering, JSCE, 523(3–33), 133–140. (In Japanese) [20] Shuangyang Li, Mingyi Zhang, YibinTian, Wansheng Pei, HuaZhong, 2015. Experimental and numerical investigations on frost damage mechanism of a canal in cold regions. Cold Regions Science and Technology, 116, 1–11. [21] Tong Chang Jian, Shen ZongYan, 1982. Horizontal frost heave thrust acting on buttress constructions. Developments in Geotechnical Engineering, 28, 259–268. [22] Tian-liang Wang, Yao-jun Liu, Han Yan, Lei Xu, 2015. An experimental study on the mechanical properties of silty soils under repeated freeze-thaw cycles. Cold Regions Science and Technology, 112, 51–65.

T

[23] Uno, H., Suzuki, T., Sawada, S. 2002. A countermeasure to frost heave of multi-anchored retaining wall in cold region. Journal of Geotechnical Engineering, JSCE, 701(3–58), 243一252. (In Japanese)

IP

[24] Yuanming Lai, Shi min Zhang, Wenbing Yu, 2012. A new structure to control frost boiling and frost heave of embankments in cold regions. Cold Regions Science and Technology, 79–80, 53–66.

SC R

[25] Yokota, Y., Maeda, Y., Ochiai, H., Omine K., 2002. The characteristics of the bearing capacity on the improvement ground with mixed plastic chips. The Japanese Society of Civil Engineers,701(3–58), 87–87.

[26] Zhuo Li, Sihong Liu, Liujiang Wang, Chenchen Zhang, 2013. Experimental study on the effect of frost heave prevention using soil bags. Cold Regions Science and

AC

CE P

TE

D

MA

NU

Technology, 85, 109–116.

18

ACCEPTED MANUSCRIPT Abbreviation

1) EPS, expanded poly-styrene; FI, freezing index; KIT, Kitami Institute of Technology;

AC

CE P

TE

D

MA

NU

SC R

IP

T

2）σx, the horizontal frost force; σn, normal frost-heave force; σy, vertical component;

19

ACCEPTED MANUSCRIPT Highlights 2) Frost-heave mechanism is gained by freezing front distribution and behavior of walls. 3）The effectiveness of the replacement method and the insulation method are verified.

IP

T

4）A method for determining effective replacement zone of backfill soils is proposed.

SC R

5）The feasibility of granular material used as replacement material is verified.

AC

CE P

TE

D

MA

NU

5）Horizontal component of frost heaving force acting on vertical wall is considered.

20