Experimental Study On Creep Characteristics Of Soft-hard Interbedded Rock-like Materials Under Biaxial Compression

Under the action of long and complex geological structure,there are a wide range of composite bedded rock bodies in nature,which are usually composed of rocks of different lithology alternately,and the combination between layers is very close.Different from the rock mass with single lithology,the layered composite rock mass has significant discontinuity,heterogeneity and anisotropy,and its mechanical properties are not only affected by the different lithology and rock strata of the interbedded rock mass,but also affected by the mechanical properties of the structural plane of each bedding plane.The long-term stability of layered rock mass is closely related to the rheological properties of rock,and its long-term stability is very important for the stability and safety of rock mass engineering.At present,there is still a great space for research on the creep properties of interlayered rock mass.Based on the similar material,the simulation made a stratified sample,such as rock,hard and soft through mutual laminated materials,such as rock,hard and soft biaxial creep test research,establish mutual laminated materials,such as rock,hard and soft creep under the condition of biaxial compression creep constitutive model,the research analyzes the mutual laminated materials,such as rock,hard and soft biaxial creep mechanical properties.The main research work is as follows:(1)The mold for making soft and hard interbedded rock samples was designed and processed,using ordinary Portland cement,quartz sand,gypsum,such as material,through a series of matching test,the configuration of two different mechanical properties of similar material,the two similar material made into a single class of rock specimens respectively,conducted a series of basic mechanics performance test,The basic physical and mechanical properties of two similar materials were obtained,and the interbedded rock composed of these two materials with different mechanical properties was prepared.The uniaxial compressive strength of the interbedded rock samples was obtained by uniaxial compression tests,and the failure characteristics of the samples were analyzed.(2)The biaxial compression creep tests of soft and hard interbedded rocks composed of these two materials with similar mechanical properties were carried out.It is found that the creep of soft and hard interbedded rock materials includes three stages: decelerated creep,isometric creep and accelerated creep.Decelerated creep and isometric creep account for a large proportion,while accelerated creep account for a small proportion.With the increase of lateral stress,the creep failure strength decreases gradually,while the creep strain increase rate increases.The creep characteristics of specimens are significantly affected by different stress levels.When the lateral stress is the same,the axial strain increases with the increase of axial stress.When the axial stress is the same,the axial strain and lateral strain decrease first and then increase with the increase of lateral stress.DIC technology was used to monitor the surface deformation of the sample.It was found that when the lateral stress level was low,the axial strain of the sample mainly depended on the hard rock.When the lateral stress level exceeded the compressive strength of the soft rock,the cracks in the soft rock would lead to the macroscopic failure of the sample in advance..(3)The basic components of the creep constitutive model are qualitatively identified by analyzing the curve characteristics of the axial creep samples of soft and hard interbedded rocks,and the Cvisc creep constitutive model which can reflect the decelerated creep,constant creep and accelerated creep is adopted.The levenberg-Marquardt algorithm in Origin was used to fit the experimental curve of axial creep,and the parameters of creep constitutive model and creep constitutive equation of samples under different stresses were obtained.The Cvise creep constitutive model can reasonably describe the creep characteristics of soft and hard interbedded rocks.There are 59 figures,15 tables and 99 references...