Study On Failure Mechanism Of Weakening Anchoring Interface In Weakly Cemented Soft Rock Stratum With Rich Water

Due to its special diagenetic environment and sedimentary history,weakly cemented soft rock shows unique physical and mechanical properties such as low strength,poor cementation,easy weathering and cement disintegration,especially under the influence of groundwater,its mechanical properties are more unstable.It results in the poor anchoring ability,low anchoring force and easy failure of bolt(cable)support in weakly cemented soft rock stratum under water-enriched condition.In view of the above problems,the weakening failure mechanism of the anchoring interface in the weakly cemented soft rock stratum under water-enriched condition is clarified,the factors affecting the stability of the anchoring interface are analyzed,and the corresponding measures are put forward,which is of great significance to the safety construction and protection of the weakly cemented soft rock stratum engineering under water-enriched condition.In this paper,based on the indoor shear test of anchorage interface,through numerical simulation and theoretical analysis,the weakening failure mechanism of anchorage interface in weakly cemented soft rock stratum under water-enriched condition is studied comprehensively and deeply.The main work of this paper are as follows:1.Develop weak cemented soft rock simulation materials and carry out laboratory shear tests on the weakening characteristics of anchoring interface strength in weakly cemented soft rock strata under water-enriched condition.Research and development,comparison and selection of weakly cemented soft rock simulation materials and immersion mechanical property tests are carried out.The relationship between immersion time and water content and uniaxial compressive strength is studied.The function expression between immersion time and water content and uniaxial compressive strength is obtained by fitting.A model of weakly cemented soft rock anchoring interface unit is proposed.Shear tests of weakly cemented soft rock anchoring interface unit under different soaking times are carried out.The shear stress-shear displacement relationship of anchoring interface under different soaking times and the weakening characteristics of water content on anchoring interface strength parameters are analyzed.2.The bond-slip constitutive model of anchoring interface in weakly cemented soft rock stratum under water-enriched condition is established and embedded in FLAC-3D software.Based on the experimental analysis results and considering the dilatancy effect at the anchorage body interface,a constitutive model used to describe the progress of elastic,dilatancy hardening,debonding of anchoring interface in weakly cemented soft rock stratum under water-enriched condition is proposed.The interface unit in FLAC-3D software is modified by writing FISH language,and the numerical simulation results are compared with the shear test results for verification and analysis.3.Carry out the whole-course theoretical analysis of weakening failure of anchoring interface in weakly cemented soft rock stratum under water-enriched condition.Based on the experimental analysis results and the proposed constitutive model used to describe the progress of elastic,dilatancy hardening,debonding of anchoring interface in water-rich weakly cemented soft rock stratum,the full-course analysis model of anchoring body interface is constructed by load transfer method,the full-course theoretical analysis method of weakening failure of anchoring interface in water-enriched weakly cemented soft rock stratum under pull-out load is established,and the influencing factors of ultimate pull-out load,shear stress and axial force of anchoring body interface are analyzed.