Study On Mechanical Properties And Constitutive Model Of Layered Composite Rockk Under Static Load

With the rapid development of national economy and scientific technology,the earth's surface shallow resources are constantly exhausted,and the development and utilization of underground space has become very urgent.The complex and changeable perfomance of deep underground space and the harsh underground engineering surroundings bring various challenges to scientific research and practical engineering production.Complex rock is a kind of common rock mass with obvious layered structure in deep underground engineering.After a long period of geological structure and strata movement,it forms layered rock mass with complex structural planes such as folds,faults,bedding and joints,and influences each layer on orientation,angle and density.Therefore,Due to the existence of complex interface layer between rocks with different lithology and between rocks with the same lithology,the interface layer or bedrock near the interface layer will be destructed in part or as a whole,and ultimately affect the performance of the whole rock mass.Therefore,the study of interface mechanics has become an significant part in the study of deep rock mass.The study of interface mechanics has become an significant part in the study of deep rock mass.In this paper,deep rock is selected as raw material,processes into layered composite rock with different interface dip angles and carries out static mechanical test to further study its mechanical properties and constitutive relationship.The main contents and achievements of the research work include:(1)Red sandstone and green sandstone are selected as the initial materials.The cut rock samples are bonded by dolomite glue to make five kinds of layered composite rocks with dip angles of 0°,15°,30°,45°and 60°.(2)Through uniaxial compression test and triaxial uniaxial test on the layered composite rock,all kinds of relationship between one-dimensional stress and three-dimensional stress is obtained.Then study the failure mode of layered composite rock.(3)The influence of interface layer on the compressive strength of rock is analyzed.The result shows that 0 ° and 15 ° interface dip angle is close to the uniaxial compressive strength of layered composite rock.The uniaxial compressive strength of layered composite rock with 30° interface dip angle is smaller than that of layer ed composite rock with 0° and 15° interface dip angle,but the difference is not prominent.The layered composite samples with 45°and 60°dip angles are much smaller than those with 15°and 0°dip angles.The test results show that the bearing capacity of layered composite rock with 45°and 60°interface dip angle does not reach the failure strength of bedrock when they are destrcuted.The results are caused by the failure of interface sliding.(4)Based on the Weibull probability density function and the Drucker-Prager criterion,a stratified model of layered composite rock with a certain interface layer dip angle is established.By comparing the model fitting curve with the test curve,the results show that the model curve is consistent with the test curve,so a s to verify the correctness and rationality of the model.