Study On Creep Failure Evolution Mechanism Of Multi-weak Layers Soft Rock Slope In Open Pit Mine

Mineral resources have long been regarded as the cornerstone of China’s economic development.The problem of creep failure of multi-weak layer soft rock slope in open pit mine has also attracted extensive attention of scholars at home and abroad.Therefore,the research on the creep characteristics of multi-weak layer soft rock slope in open pit mine has very important practical significance.In this thesis,the mudstone in the soft rock slope of Fushun open pit mine is taken as the research object.A nonlinear creep constitutive model suitable for the mudstone in the soft rock slope of the Fushun open-pit mine is established through its laboratory mechanical test and creep mechanical test.The parameters of the creep constitutive model are calibrated by MATLAB data analysis software.Through the second developed UMAT subroutine,the creep constitutive model is used to simulate the complete creep process of mudstone,the time hardening model in ABAQUS finite element software is applied to simulate the creep process of soft rock slope in the Fushun open pit mine.The specific research contents are as follows:(1)By studying the mechanical properties and creep theory of rock,the creep constitutive model of mudstone applied to multi-weak layer soft rock slope in Fushun open pit mine,namely the improved Burgers model,is obtained.(2)The mudstone specimens obtained from the soft rock slope of Fushun open pit mine are tested for uniaxial compressive strength of mudstone under different freeze-thaw cycles,the stress-strain curves of mudstone under different freeze-thaw cycles are obtained,the loading order and stress level in uniaxial compression creep test are determined,and then the uniaxial compression creep test of mudstone is carried out to obtain the creep curve of mudstone,The parameters of the improved Burgers model are determined by MATLAB data analysis software.(3)The UMAT subroutine corresponding to the improved Burgers model is compiled by using Fortran language,and then put into ABAQUS to simulate the uniaxial compression creep test of mudstone under 5MPa.The simulation results are compared with the test results,and the correctness and applicability of the compiled UMAT subroutine are verified according to the degree of coincidence between the two;(4)The time hardening model in ABAQUS finite element software is used to simulate the uniaxial compression creep test of mudstone at 3Mpa.The simulated result is compared with the test result to verify the applicability of the time hardening model.The time hardening model is applied to simulate the creep process of soft rock slope of Fushun open pit mine in100 years under three different weak layer numbers,The influence of the number of weak layer on the creep of soft rock slope in Fushun open pit mine is studied.To sum up,under the background of multi-weak layer soft rock slope engineering in Fushun open pit mine,firstly,it is proved that the UMAT subroutine corresponding to the self-made improved Burgers model can be used to study the creep characteristics of mudstone;Secondly,it is verified that the time hardening model in ABAQUS finite element software can be used to study the creep characteristics of multi-weak layers soft rock slope in Fushun open pit mine;Finally,through the simulation study on the creep process of multi-weak layers soft rock slope in Fushun open pit mine in the past 100 years,it is confirmed that the existence of multi-weak layer will increase the creep deformation of soft rock slope in Fushun open pit mine.