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Why are crack paths in concrete and mortar different from those in PMMA?
287A
Influence of dynamic loads 895471 Dynamic loading of buried structures Davies, M C F Prac lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2. P250-254. Publ Edinburgh: Engineering Technics Press, 1987 Model tests on metal tubes embedded in sand were used to study the influence of cover depth on load to failure for static surface loading and dynamic loading by a falling weight. Peak dynamic surface pressure at failure was greater than the static value. The natural frequency of the soil structure system was calculated using the Rayleigh method and used to evaluate the dynamic magnification factor. Values of peak dynamic load predicted using this method agree well with experimental results. 895472 Dynamic soil structure interaction of masonry sewers Sibbald, A; Forde, M C Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2. P255-266. Publ Edinburgh: Engineering Technics Press. 1987 A program to investigate the feasibility of using specific sonic and transient shock non-destructive tests to test structural integrity of brick lined tunnels is described. Tests in both time and frequency domains are discussed. Field tests and tests on a laboratory model, test equipment, and test procedure are described. A simple and rapid test was developed. 895473 Earthquake resistant design of tunnels Srivastava, L S Proc International Symposium Tunnelling for Water Resources and Power Projects, New Delhi, 19-23 January 1988 VI, P!21-124. Publ Net; Delhi." Oxford and IBH Publishing Co, 1988 Design of tunnels in earthquake prone areas is discussed. The potential effect of an earthquake on the tunnel and the behaviour of the tunnel during earthquakes is described. The risk to tunnel safety is dependent on rock type and tunnel depth. Design criteria are presented, with the main objective being to have enough flexibility to absorb imposed deformation without losing the capacity to carry static loads. 895474 Excess Shear Stress (E.S.S.). A case study Holmes, R D; Reeson, J A Proc 2nd International Symposium of Rockbursts and Seismicity in Mines, Minneapolis, 8-10 June 1988 P475-487. Publ Minneapolis: University of Minnesota, 1988 A relatively high level of seismicity has been experienced in the Buffelfontein gold mine, South Africa. Investigations were undertaken to establish correlations between state of Excess Shear Stress (driving shear stress on a fault minus dynamic shear strength of the fault) and physical parameters such as length of fault exposed by mining and area of mining, and to link ESS with seismicity. The stress analysis program MINSIM D Phase III was used to model sequence of mining from
1977 to 1987. Results may be used to provide a design tool for extraction sequence and support in mines which experience severe seismicity.
Subjects Peripheral to Geomechanics Fracture mechanics 895475 Fracture toughness of geomaterials. Applications brief Siriwardane, H J; Layne, A W lnt J Num Anal Meth Geomech VI3, N2, March-April 1989, P199-205 Fracture mechanics has many applications to geomechanics. The ASTM Standard E399 for determination of Mode I fracture toughness, developed for metals, is not suitable for core based geological samples. The short-rod test configuration of Barker (1977) is introduced. Geometric details, theoretical basis and finite element calibration are examined, and its applicability to fracture toughness problems in geomechanics discussed. 895476 Load effects on fracture of concrete Sri Ravindrarajah, R; Swamy, R N Mater Struct V22. N127. Jan 1989. P15-22 The concrete system contains a network of microcracks even before application of external load. The multiplication, growth, and precipitation of the microcracks at high strains leads to visible fractures. The formation of microcracks under constant and short term loading has been studied in the laboratory. Results show that, at equal strain, degree of internal microcracking is significantly reduced if load is applied over a period of time rather than in one step. The improvement in crack resistance of concrete due to creep, and the contribution of microcracking to creep deformation are also discussed. 895477 Why are crack paths in concrete and mortar different from those in PMMA? Melin, S Mater Struct V22. N127, Jan 1989. P23-27 Experiments in concrete and mortar suggest that crack growth does not necessarily take place under Mode I conditions. Experiments were repeated using plexiglass specimens of similar geometry to examine the influence of material type on crack propagation. Numerical modelling assuming Mode I growth was also carried out. Laboratory results on the plastic agree with finite element simulation, but differ significantly from those from concrete. It is concluded that small scale yielding conditions are not well realized in concrete, and a large process region of small cracks influences crack growth.
© 1989 Pergamon Press plc. Reproduction notpermitted
Influence of dynamic loads 895471 Dynamic loading of buried structures Davies, M C F Prac lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2. P250-254. Publ Edinburgh: Engineering Technics Press, 1987 Model tests on metal tubes embedded in sand were used to study the influence of cover depth on load to failure for static surface loading and dynamic loading by a falling weight. Peak dynamic surface pressure at failure was greater than the static value. The natural frequency of the soil structure system was calculated using the Rayleigh method and used to evaluate the dynamic magnification factor. Values of peak dynamic load predicted using this method agree well with experimental results. 895472 Dynamic soil structure interaction of masonry sewers Sibbald, A; Forde, M C Proc lnt Conference on Foundations and Tunnels, London, 2426 March 1987 V2. P255-266. Publ Edinburgh: Engineering Technics Press. 1987 A program to investigate the feasibility of using specific sonic and transient shock non-destructive tests to test structural integrity of brick lined tunnels is described. Tests in both time and frequency domains are discussed. Field tests and tests on a laboratory model, test equipment, and test procedure are described. A simple and rapid test was developed. 895473 Earthquake resistant design of tunnels Srivastava, L S Proc International Symposium Tunnelling for Water Resources and Power Projects, New Delhi, 19-23 January 1988 VI, P!21-124. Publ Net; Delhi." Oxford and IBH Publishing Co, 1988 Design of tunnels in earthquake prone areas is discussed. The potential effect of an earthquake on the tunnel and the behaviour of the tunnel during earthquakes is described. The risk to tunnel safety is dependent on rock type and tunnel depth. Design criteria are presented, with the main objective being to have enough flexibility to absorb imposed deformation without losing the capacity to carry static loads. 895474 Excess Shear Stress (E.S.S.). A case study Holmes, R D; Reeson, J A Proc 2nd International Symposium of Rockbursts and Seismicity in Mines, Minneapolis, 8-10 June 1988 P475-487. Publ Minneapolis: University of Minnesota, 1988 A relatively high level of seismicity has been experienced in the Buffelfontein gold mine, South Africa. Investigations were undertaken to establish correlations between state of Excess Shear Stress (driving shear stress on a fault minus dynamic shear strength of the fault) and physical parameters such as length of fault exposed by mining and area of mining, and to link ESS with seismicity. The stress analysis program MINSIM D Phase III was used to model sequence of mining from
1977 to 1987. Results may be used to provide a design tool for extraction sequence and support in mines which experience severe seismicity.
Subjects Peripheral to Geomechanics Fracture mechanics 895475 Fracture toughness of geomaterials. Applications brief Siriwardane, H J; Layne, A W lnt J Num Anal Meth Geomech VI3, N2, March-April 1989, P199-205 Fracture mechanics has many applications to geomechanics. The ASTM Standard E399 for determination of Mode I fracture toughness, developed for metals, is not suitable for core based geological samples. The short-rod test configuration of Barker (1977) is introduced. Geometric details, theoretical basis and finite element calibration are examined, and its applicability to fracture toughness problems in geomechanics discussed. 895476 Load effects on fracture of concrete Sri Ravindrarajah, R; Swamy, R N Mater Struct V22. N127. Jan 1989. P15-22 The concrete system contains a network of microcracks even before application of external load. The multiplication, growth, and precipitation of the microcracks at high strains leads to visible fractures. The formation of microcracks under constant and short term loading has been studied in the laboratory. Results show that, at equal strain, degree of internal microcracking is significantly reduced if load is applied over a period of time rather than in one step. The improvement in crack resistance of concrete due to creep, and the contribution of microcracking to creep deformation are also discussed. 895477 Why are crack paths in concrete and mortar different from those in PMMA? Melin, S Mater Struct V22. N127, Jan 1989. P23-27 Experiments in concrete and mortar suggest that crack growth does not necessarily take place under Mode I conditions. Experiments were repeated using plexiglass specimens of similar geometry to examine the influence of material type on crack propagation. Numerical modelling assuming Mode I growth was also carried out. Laboratory results on the plastic agree with finite element simulation, but differ significantly from those from concrete. It is concluded that small scale yielding conditions are not well realized in concrete, and a large process region of small cracks influences crack growth.
© 1989 Pergamon Press plc. Reproduction notpermitted