- Email: [email protected]
Pelton landslide: an unusual double-wedge failure
195A chosen treatment, on the basis of costs and construction control, being excavation to below the shear plane in bays not exceeding 15m and excavation support by driven H piles.
933431 Slope mabtlimtion experience in Somh Wales, UK Jones, D B
Proc Conference on Slope Stability Eagi~eri~: DevelOpments and Applications,Isleof Wigkt, 15-18 April 1991 P313-320. Publ London." Thomas Telford,1991 Many valley areas of South Wales show slope stability problems due to a combination of inherent geological factors, past mining activity, and past and present excavations in lower valley slopes. Practical slope engineering in these areas requires a multidisciplinary approach. The development of an engineering database and archive library of landslides in the Rhondda Valley is described. Computed factors of safety and required corrective measures are discussed. The importance of gaining the confidence of the local community is considered. Success can be quantified in terms of stability achieved, design life and maintenance, cost, and public acceptance.
933432 Evalution of slope stability - a 25 year perspective Morgenstern, N R
Proc Conference Stability and Performance of Slopes and Embankments II, Berkeley, 29 Jmte-I July 1992 V1, P1-26. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) Developments in slope stability analysis in the period since the 1966 ASCE Conference are outlined. The requirements for evaluation of slope stability are listed: site characterisation; mode identification; material characterisation; pore pressure characterisation; and analytical model. Global stability analysis procedures, deformation analysis, and problem oriented classification of slopes are examined. Factors influencing slope stability are then considered for compacted soils and waste dumps and for natural slopes, including coarse grained soils, unsaturated soils, and natural contractant and dilatant clays. 82 refs
933433
St~inty analy~ of an earth slope Lambe, T W; Sflva-Tulla, F
Proc Conference Stability ~ Performsmee of Slopes and Embakments II, Berkeley, 29 Jane-1 July 1992 V1, P27-69. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) A stability approach based on stress paths is presented. It consists of the following stages: preparation of preliminary stress paths to guide analysis; selection of slope geometry for analysis; determination of average shear and normal stresses acting on the critical surface; determination of average pore pressure acting on the critical surface at stages of interest; determination of average strength of the critical surface; and evaluation of safety factors. Applied correctly, all common methods of slope analysis give the correct average shear stress. The ordinary method of slices gives a lower value of average normal stress than do more rigorous methods, and a compensating correcting factor is presented. The same factor of safety can be obtained by effective stress or total stress analysis, but the former can handle a greater range of problems and allows improved understanding of the stability.
933434
Zull 1 ~ ond hmd~ge hJmml Thiers, G R; Benfer, A; Merida, L; Grass, R
Proe Conference Stability awl P e r f ~ e of Slopes o~! Emba~mmts 11, Berkeley, 29 Jae-I July 1992 V1, P205221. PUbl New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) A major landslide in the Zunil 1 geothermal field in Guatemala in 1991 caused loss of life and severe damage to well ZCQ-4. Geology and topography of the region are illustrated. Examination of the material covering the well and analysis of geological data indicated failure was fairly shallow and the result of a combination of seepage water and steep slopes reactivating a historic landslide. Hazard mapping of the field has been carried out. The well ZCQ-4 has subsequently been capped and further developments will be undertaken in areas of lower landslide hazard. 933435 State-of-the-art: static stability and deformation mmlysis
Duncan, J M
Proc Conference Stability and Perfornumce of Slopes and Embankments II, Berkeley, 29 JMe-I July 1992 V1, P222266. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) In the past 25 years, the widespread availability of the PC and improved understanding of constitutive behaviour of soils have made numerical analysis of slope stability problems a practical proposition for the engineer. A review of these developments is presented. Current formulation of the problem is first considered. Practical methods of slope analysis, including 3D analysis and analysis for reinforced slopes, the range of constitutive models and their applications, and the many computer codes available for slope analysis are discussed. Examples of their use for cases of earth dam slopes are illustrated. 177 refs 933436
Study of slope ggl~ifity analysis Deschamps, R J; Leonards, G A
Proe Comferemee Stability and Performance of Slopes and Embankments II, Berkeley, 29 Jane-I JMy 1992 V1, P267291. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) The stability of earth slopes is dependent on initial state of stress and the stress path experienced during slope construction. These factors are not considered in limit equilibrium analysis, which also assumes a constant safety factor along candidate slip surfaces. A study which deals with these factors is presented. It uses the finite element code CRISP and the Cam-Clay constitutive model. A new index of safety is introduced to account for variable safety factors along the slip surface. Example problems are solved and results compared with those of LEA (simplified Bishop) analysis. 933437
Pelton ~ : an anmnal donble-wedge fallare Cornforth, D H; Vessely, D A Proc Conference Stability and Performance of Slopes and E m b a k m e m s II, Berkeley, 29 JBe-I J~y 1992 VI, P310324. Publ New York: ASCE, 1992 (ASCE Special Geotechnical PublicationNo 31) A landslide occurred on a slope above the Pelton Dam, Oregon, in 1975. Initial horizontal movement of 90mm/week
slowed to almost zero in 1988. Excavation of landslide debris to improve safety in 1990 instead reactivated the slide. Investigations revealed a double-wedge failure with a horizontal basal plane. The headscarp was a pre-existing steeply inclined
© 1993 Pergamon Press Ltd. Reproduction not permitted RMMS 30/3--N
196A plane. The lower wedge was failing within a weathered, weakly cemented sedimentary stratum. Delayed failure as a result of construction works some 66 years earlier is suggested as the reason for slope instability. Stabilisation was achieved by transfer of material from the upper driving wedge to the lower resistive wedge.
933438 Interslice force functions for limit equilibrium analysis Rahardjo, H; Fredlund, D G; Fan, K K Proc Conference Stability and Performance of Slopes and Embankments I1, Berkeley, 29 Jane-1 July 1992 VI, P325341. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) The limit equilibrium method of slices is commonly used in slope analysis. Its indeterminacy is generally resolved by using an assumption regarding interslice forces. Appropriate interslice force functions have been predicted using finite element analysis. A bell-shaped function is found for simple homogeneous slopes with circular slip surfaces. For active lateral earth pressure problems, the interslice force function is essentially triangular. For passive earth pressure problems, high stress is found close to the wall, diminishing to zero some distance from the wall.
933439 Application of rock engineering to pit slope optim~tion at De Hock Terbrugge, P J; Langenhoven, E M Proc SANGORM Symposium on Impact of Rock Engintering on Mining and Tuanelliq Economics, Weikom, 7-8 October 1991 P79-82. Publ SANGORM: Orange Grove, 1991 The De Hoek limestone quarry exploits an orebody of intercalated limestone and phyllite dipping in an easterly direction at angles between 30 and 50 deg. Rock engineering principles have been applied to design of both footwall and hangingwall slopes. The former is largely controlled by structural geology. Mining is restricted to individual benches on prominent horizons with a high degree of control on the drilling and blasting program. The hangingwall slope is comprised primarily of phyllites and has an overall slope angle of 59 deg. Controlled blasting is used to minimise damage and slope monitoring to ensure safety. Steep slopes enable increased recovery with reduced stripping.
E a r t h retaining s t r u c t u r e s See also: 933331 933440 Efficient three-dimensional soft-structure interaction model for
analysis of earth retaining mu,Ymres
Vaziri, H H; Troughton, V M Can Geotech J V29, N4, Aug 1992, 1'529-538 Using the integrated form of Mindlin's equations, a numerical model is developed for analysis of earth pressure problems for structures such as sheet piles or diaphragm walls. The model is intermediate in cost and complexity between 3D nonlinear finite element analyses and modulus of subgrade reaction approaches, but gives results comparable to those of the finite element solution under plane strain conditions. Its use both as a predictive tool and in sensitivity analysis to control mode and magnitude of wall displacement is illustrated.
933441 Transient analysis of excavations in soils Holt, D A; Grifliths, D V Comput Geotech V13, N3, 1992, P159-174 Finite element analysis of the transient stability of an excavation in an elastoplastic soil is presented. The excavation steps are rigorously modelled with transient effects included using a fully coupled Biot formulation. Stability is shown to be a function of rate of excavation, soil permeability, and length of drainage paths. Critical depth under various conditions is evaluated. Drained and undrained behaviours are retrieved as special cases of the transient analysis. Comparisons are made with classical solutions. 933442 Earthquake resistant design of earth walls - a prohabmstic approach Genske, D; Klapperich, H; Adachi, T; Sugito, M Proc Fifth lnterantimud Comference on Soil Dymandcs and Earthquake Engineering, Karismbe, 23-26 September 1991 P403-414. Publ Southampton: Computational Mechanics Publications, 1991 / The design of reinforced earth retaining walls depends strongly on the safety factors used in the stability analysis. Because of the complexity of the problem when seismic forces are introduced and the incomplete knowledge of mechanical behaviour of the geotextile and the failure mechanisms, a probabilistic approach is recommended. The failure mode considered here has the failure plane cutting through the geotextile layers. Parametric studies indicate the toe of the wall is the most sensitive part. Reliability analysis is carried out and design factors derived.
Groundwater problems 933443 Similority of internal stability criteria for granular softs. Note Chapuis, R P Can Geotech J V29, N4, Aug 1992, P711-713 Filter criteria provide practical rules to prevent migration of fine material between adjacent layers in a soil mass. Internal instability can lead to segregation, with potential deleterious effects. Three commonly used criteria for granular soils are examined. It is shown that they can all take similar mathematical forms where the secant slope of the grain size distribution curve indicates risk of instability. 93~A.~.A. Large landslide stabilization by deep drainage wells Bianco, B; Bruce, D A Proc Conference on Slope Stability F_~gueeriag: De~elopmems a~l Applleatlo~, Isle of WigM, 15-18 April 1991 P341-348. Publ London: Thomas Telford, 1991 Traditional landsfide drainage solutions, small diameter drains and dewatering wells, are not generally applicable where deep and extensive unstable masses are met or in some sensitive urban environments. In such cases the RODREN system may be applicable. This involves drilling large (up to 2m diameter) deep shafts at 5-20m centres. Horizontal holes drilled just above shaft bottom interconnect the shafts. Any water intercepted can be transmitted by gravity to a convenient draw point. The RODREN technique allows a flexible array geometry which can be readily modified and adapted to site conditions.
© 1993 Pergamon Press Ltd. Reproduction not permitted
933431 Slope mabtlimtion experience in Somh Wales, UK Jones, D B
Proc Conference on Slope Stability Eagi~eri~: DevelOpments and Applications,Isleof Wigkt, 15-18 April 1991 P313-320. Publ London." Thomas Telford,1991 Many valley areas of South Wales show slope stability problems due to a combination of inherent geological factors, past mining activity, and past and present excavations in lower valley slopes. Practical slope engineering in these areas requires a multidisciplinary approach. The development of an engineering database and archive library of landslides in the Rhondda Valley is described. Computed factors of safety and required corrective measures are discussed. The importance of gaining the confidence of the local community is considered. Success can be quantified in terms of stability achieved, design life and maintenance, cost, and public acceptance.
933432 Evalution of slope stability - a 25 year perspective Morgenstern, N R
Proc Conference Stability and Performance of Slopes and Embankments II, Berkeley, 29 Jmte-I July 1992 V1, P1-26. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) Developments in slope stability analysis in the period since the 1966 ASCE Conference are outlined. The requirements for evaluation of slope stability are listed: site characterisation; mode identification; material characterisation; pore pressure characterisation; and analytical model. Global stability analysis procedures, deformation analysis, and problem oriented classification of slopes are examined. Factors influencing slope stability are then considered for compacted soils and waste dumps and for natural slopes, including coarse grained soils, unsaturated soils, and natural contractant and dilatant clays. 82 refs
933433
St~inty analy~ of an earth slope Lambe, T W; Sflva-Tulla, F
Proc Conference Stability ~ Performsmee of Slopes and Embakments II, Berkeley, 29 Jane-1 July 1992 V1, P27-69. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) A stability approach based on stress paths is presented. It consists of the following stages: preparation of preliminary stress paths to guide analysis; selection of slope geometry for analysis; determination of average shear and normal stresses acting on the critical surface; determination of average pore pressure acting on the critical surface at stages of interest; determination of average strength of the critical surface; and evaluation of safety factors. Applied correctly, all common methods of slope analysis give the correct average shear stress. The ordinary method of slices gives a lower value of average normal stress than do more rigorous methods, and a compensating correcting factor is presented. The same factor of safety can be obtained by effective stress or total stress analysis, but the former can handle a greater range of problems and allows improved understanding of the stability.
933434
Zull 1 ~ ond hmd~ge hJmml Thiers, G R; Benfer, A; Merida, L; Grass, R
Proe Conference Stability awl P e r f ~ e of Slopes o~! Emba~mmts 11, Berkeley, 29 Jae-I July 1992 V1, P205221. PUbl New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) A major landslide in the Zunil 1 geothermal field in Guatemala in 1991 caused loss of life and severe damage to well ZCQ-4. Geology and topography of the region are illustrated. Examination of the material covering the well and analysis of geological data indicated failure was fairly shallow and the result of a combination of seepage water and steep slopes reactivating a historic landslide. Hazard mapping of the field has been carried out. The well ZCQ-4 has subsequently been capped and further developments will be undertaken in areas of lower landslide hazard. 933435 State-of-the-art: static stability and deformation mmlysis
Duncan, J M
Proc Conference Stability and Perfornumce of Slopes and Embankments II, Berkeley, 29 JMe-I July 1992 V1, P222266. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) In the past 25 years, the widespread availability of the PC and improved understanding of constitutive behaviour of soils have made numerical analysis of slope stability problems a practical proposition for the engineer. A review of these developments is presented. Current formulation of the problem is first considered. Practical methods of slope analysis, including 3D analysis and analysis for reinforced slopes, the range of constitutive models and their applications, and the many computer codes available for slope analysis are discussed. Examples of their use for cases of earth dam slopes are illustrated. 177 refs 933436
Study of slope ggl~ifity analysis Deschamps, R J; Leonards, G A
Proe Comferemee Stability and Performance of Slopes and Embankments II, Berkeley, 29 Jane-I JMy 1992 V1, P267291. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) The stability of earth slopes is dependent on initial state of stress and the stress path experienced during slope construction. These factors are not considered in limit equilibrium analysis, which also assumes a constant safety factor along candidate slip surfaces. A study which deals with these factors is presented. It uses the finite element code CRISP and the Cam-Clay constitutive model. A new index of safety is introduced to account for variable safety factors along the slip surface. Example problems are solved and results compared with those of LEA (simplified Bishop) analysis. 933437
Pelton ~ : an anmnal donble-wedge fallare Cornforth, D H; Vessely, D A Proc Conference Stability and Performance of Slopes and E m b a k m e m s II, Berkeley, 29 JBe-I J~y 1992 VI, P310324. Publ New York: ASCE, 1992 (ASCE Special Geotechnical PublicationNo 31) A landslide occurred on a slope above the Pelton Dam, Oregon, in 1975. Initial horizontal movement of 90mm/week
slowed to almost zero in 1988. Excavation of landslide debris to improve safety in 1990 instead reactivated the slide. Investigations revealed a double-wedge failure with a horizontal basal plane. The headscarp was a pre-existing steeply inclined
© 1993 Pergamon Press Ltd. Reproduction not permitted RMMS 30/3--N
196A plane. The lower wedge was failing within a weathered, weakly cemented sedimentary stratum. Delayed failure as a result of construction works some 66 years earlier is suggested as the reason for slope instability. Stabilisation was achieved by transfer of material from the upper driving wedge to the lower resistive wedge.
933438 Interslice force functions for limit equilibrium analysis Rahardjo, H; Fredlund, D G; Fan, K K Proc Conference Stability and Performance of Slopes and Embankments I1, Berkeley, 29 Jane-1 July 1992 VI, P325341. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31) The limit equilibrium method of slices is commonly used in slope analysis. Its indeterminacy is generally resolved by using an assumption regarding interslice forces. Appropriate interslice force functions have been predicted using finite element analysis. A bell-shaped function is found for simple homogeneous slopes with circular slip surfaces. For active lateral earth pressure problems, the interslice force function is essentially triangular. For passive earth pressure problems, high stress is found close to the wall, diminishing to zero some distance from the wall.
933439 Application of rock engineering to pit slope optim~tion at De Hock Terbrugge, P J; Langenhoven, E M Proc SANGORM Symposium on Impact of Rock Engintering on Mining and Tuanelliq Economics, Weikom, 7-8 October 1991 P79-82. Publ SANGORM: Orange Grove, 1991 The De Hoek limestone quarry exploits an orebody of intercalated limestone and phyllite dipping in an easterly direction at angles between 30 and 50 deg. Rock engineering principles have been applied to design of both footwall and hangingwall slopes. The former is largely controlled by structural geology. Mining is restricted to individual benches on prominent horizons with a high degree of control on the drilling and blasting program. The hangingwall slope is comprised primarily of phyllites and has an overall slope angle of 59 deg. Controlled blasting is used to minimise damage and slope monitoring to ensure safety. Steep slopes enable increased recovery with reduced stripping.
E a r t h retaining s t r u c t u r e s See also: 933331 933440 Efficient three-dimensional soft-structure interaction model for
analysis of earth retaining mu,Ymres
Vaziri, H H; Troughton, V M Can Geotech J V29, N4, Aug 1992, 1'529-538 Using the integrated form of Mindlin's equations, a numerical model is developed for analysis of earth pressure problems for structures such as sheet piles or diaphragm walls. The model is intermediate in cost and complexity between 3D nonlinear finite element analyses and modulus of subgrade reaction approaches, but gives results comparable to those of the finite element solution under plane strain conditions. Its use both as a predictive tool and in sensitivity analysis to control mode and magnitude of wall displacement is illustrated.
933441 Transient analysis of excavations in soils Holt, D A; Grifliths, D V Comput Geotech V13, N3, 1992, P159-174 Finite element analysis of the transient stability of an excavation in an elastoplastic soil is presented. The excavation steps are rigorously modelled with transient effects included using a fully coupled Biot formulation. Stability is shown to be a function of rate of excavation, soil permeability, and length of drainage paths. Critical depth under various conditions is evaluated. Drained and undrained behaviours are retrieved as special cases of the transient analysis. Comparisons are made with classical solutions. 933442 Earthquake resistant design of earth walls - a prohabmstic approach Genske, D; Klapperich, H; Adachi, T; Sugito, M Proc Fifth lnterantimud Comference on Soil Dymandcs and Earthquake Engineering, Karismbe, 23-26 September 1991 P403-414. Publ Southampton: Computational Mechanics Publications, 1991 / The design of reinforced earth retaining walls depends strongly on the safety factors used in the stability analysis. Because of the complexity of the problem when seismic forces are introduced and the incomplete knowledge of mechanical behaviour of the geotextile and the failure mechanisms, a probabilistic approach is recommended. The failure mode considered here has the failure plane cutting through the geotextile layers. Parametric studies indicate the toe of the wall is the most sensitive part. Reliability analysis is carried out and design factors derived.
Groundwater problems 933443 Similority of internal stability criteria for granular softs. Note Chapuis, R P Can Geotech J V29, N4, Aug 1992, P711-713 Filter criteria provide practical rules to prevent migration of fine material between adjacent layers in a soil mass. Internal instability can lead to segregation, with potential deleterious effects. Three commonly used criteria for granular soils are examined. It is shown that they can all take similar mathematical forms where the secant slope of the grain size distribution curve indicates risk of instability. 93~A.~.A. Large landslide stabilization by deep drainage wells Bianco, B; Bruce, D A Proc Conference on Slope Stability F_~gueeriag: De~elopmems a~l Applleatlo~, Isle of WigM, 15-18 April 1991 P341-348. Publ London: Thomas Telford, 1991 Traditional landsfide drainage solutions, small diameter drains and dewatering wells, are not generally applicable where deep and extensive unstable masses are met or in some sensitive urban environments. In such cases the RODREN system may be applicable. This involves drilling large (up to 2m diameter) deep shafts at 5-20m centres. Horizontal holes drilled just above shaft bottom interconnect the shafts. Any water intercepted can be transmitted by gravity to a convenient draw point. The RODREN technique allows a flexible array geometry which can be readily modified and adapted to site conditions.
© 1993 Pergamon Press Ltd. Reproduction not permitted