Laboratory Tests And Constitutive Modeling On The Anisotropic Properties Of Soft Sedimentary Rock

The ansitropic is one of the most important characteristic of soft sedimentary rock.Nowadays,many engineering projects are carried out in soft sedimentary rock area,and it's a great challenge for the designer and constructor to deal with soft sedimentary rock.A careful study on ansitropic of soft sedimentary rock is both important to theoretical analysis and engineering practice.In order to study anisotropy properties of soft sedimentary rock,the mechanical properties of sandy mudstone in different direction are studied by test;On the other hand,anisotropic soft sedimentary rock t_ij sub-loading surface elastoplastic constitutive model is modified and loaded into FLAC3 D to simulate mechanical behavior of soft sedimentary rock.The fellowing conclusions were made in this study:?1?The conventional triaxial compression tests on specimen of sandy mudstone at different inclination angle were carried out.The effect of different angles and confining pressure on mechanical properties and deformation-failure mode are discussed.The results show that failure strength values and residual strength values at different inclination angles present like a spoon-shaped curve under one confining pressure.The increasing confining pressure would weaken sandy mudstone's degrees of anisotropy of failure strength.Based on the Mohr-Column criterion,shear strength parameters at different inclination angles also present like a spoon-shaped curve.The tests results shows that there are three different failure modes which are composite shear failure across and along bedding planes,sliding failure along bedding planes and tension-shear composite failure.Composite shear failure across and along bedding planes occurs for 0°angle and 30° angle,sliding failure along bedding planes occurs for 45°angle and 60°angle,tension-shear composite failure occurs for 60°angle.?2?Orientation tensor M in anisotropic soft sedimentary rock t_ij sub-loading surface elastoplastic constitutive model was modified in order to obtain the ture angle between normal vector of the sedimentation plane and the direcrion of the principle stresses when the direcrion of principle stresses was changed.?3?A dymanic link libiary program of anisotropic soft sedimentary rock t_ij sub-loading surface elastoplastic constitutive model was compiled using the secone development interface provided by FLAC3 D.Though unit test,the correction of program and applicability of constitutive model are veryified Then a excavation model is established and simulated through FLAC3 D software using the anisotropic soft sedimentary rock t_ij sub-loading surface elastoplastic constitutive model and the calculation result shows that the program is able to reflect the differences of the calculation results,not only between anisotropic stratum due to the deposition and isotropic stratum,but also between the anisotropic stratum with different deposition angles.