Tensile Strength In Geotechnical Engineering

The tensile strength of the rock mass is very small relative to the compressive and shear strength,and the effect of the tensile strength are usually neglected.At present,there is a number of research on the tensile strength of rock and soil mass,but less research on tensile mechanism and the progressive development of tensile and shear coupled effects.And most of the researches on tensile strength are concentrated in laboratory analysis,and the application of geotechnical engineering is less.However,in many cases there will be tension destruction at surface nearby,such as the cracks in the rear part of slope during landslides,the surface cracks before ground subsidence,and so on.For the slope engineering and shallow tunnels with certain deformation space and stress conditions,the existence of tensile cracks is often observed.And the tensile failure is more likely to occur near tall buildings.Therefore,the effect of tensile strength can not be ignored,and it is necessary to do a systematic analysis and discussion of tensile strength in geotechnical engineering.In this paper,the physical model test and numerical simulation are used to analyze the effect of tensile strength on the shallow tunnels and slope engineering.The main study work included as follows:(1)The stability and failure characteristics of the tunnel under eccentric loading are analyzed through physical model test and numerical simulation.Subject to the test conditions reasons,the rock samples with holes are used for tunnel analysis.In the model test and numerical experiments,the failure characteristics of tunnel modle under eccentric loading are analyzed.The tensile failure and tension-shear failure of the specimens were compared by the numerical simulation software RFPA to investigate the effect of tensile strength on the failure of specimens.From the analysis of the experimental results,the eccentric load affects the crack propagation and the failure characteristics of the tunnel.Although tensile strength has no significant effect on the stress-strain characteristics of the specimen,it has some influence on the compressive strength.And the tensile strength also has a great influence on the failure mode of the specimen.Only when the tensile failure is considered,the failure area and failure characteristics of the specimen can be reflected more accurately and reasonably.(2)The formation mechanism of tensile crack and the mechanism of tensile strength are analyzed,according to the stress information of the regional elements in the RFPA software and crack propagation process of tunnel model in physical experiment.And the element stress variation information of representative section are analyzed.The result of the analysis shows that tensile failure occurs before the overall failure of the specimen,and tensile failure promotes the stress transfer and the accumulation of compressive shear stress in the compression zone.The failure of the specimen is the result of the progressive action of tension and shear coupled effects.(3)The influence of tensile strength on the stability analysis of slope under different working conditions is analyzed by FLAC software through tensile-shear failure criterion and tensile failure criterion,to systematically study the application of the tensile strength of the slope,and whether it is necessary to consider the tensile failure,and under what circumstances it need to consider the tensile failure.Comparative analysis shows that considering the tensile failure criterion has little effect on the homogeneous slope,but it has a great influence on the stability of jointed rock slope.