Study On Creep Rupture Evolution Law Of Rock With Weak Layers

The rock mass with weak interlayers is a kind of layered composite rock mass that is relatively common in rock mass engineering.During the construction and operation period of the project,under the long-term action of its own weight and external environment,the rock mass with weak interlayers is prone to local or overall creep instability failure near the soft rock,and ultimately affects the performance of the entire rock mass.The structure of weak interlayers is also an important factor affecting the mechanical properties of rock masses containing weak layers.It has far-reaching practical significance to study the mechanical properties and crack propagation evolution laws of rock masses with weak layers of different structures.The paper selects sandstone and mudstone as raw materials,and sets different weak interlayer dip angles(θ=0°,15°,30°,45°),weak interlayer thickness(h=10mm,20 mm,30mm,40mm)and weak interlayer(c=1,2,3),a variety of rock samples with different structures containing weak layers were prepared,and uniaxial compression and graded loading creep experiments were performed.At the same time,acoustic emission equipment was used to collect the released rock mass during the loading process.The mechanical properties and final failure modes of rock masses with weak layers in different structures were analyzed.Based on the Airy stress function regardless of physical force,the analytical formula of the stress components of the weak interlayers was deduced,and the continuous-discontinuous method(CDEM)was used.The creep failure process of the rock mass containing weak layers was numerically simulated to explore the mechanical properties and crack evolution mechanism of the rock mass containing weak layers under different weak layer conditions.The main results and conclusions of the paper are as follows:(1)The analytical solution of the stress component of the rock with a single dip weak layer under uniaxial compression is derived,and the stress distribution of the upper interface with different dip angles and thicknesses of the weak layer is given.The bottom is more prone to failure than other areas,and the principal stress at the same position increases with the increase of the interlayer inclination and thickness,that is,the greater the interlayer inclination and thickness,the more likely the rock is to be damaged,and the uniaxial compression is given.There are four potential failure modes for rocks with weak layers.(2)By performing uniaxial compression experiments on rocks with weak layers and collecting acoustic emission signals in real time with acoustic emission equipment,the influence of weak interlayer characteristics on rock mechanical properties and failure modes is obtained.It is considered that the strength and elastic modulus of the weak layer-bearing rock decrease with the increase of the weak layer dip angle,the thickness of the weak layer and the number of the weak layer;the failure mode of the rock is related to the internal stress distribution of the weak layer during the loading process.The damage of rock is mainly concentrated in the weak interlayer area,while the hard rock is only partially damaged,and the acoustic emission source is also mainly concentrated in the weak interlayer area;the ringing count and energy count of the rock with weak layer under uniaxial compression can be divided into three parts.Typical stages:rising,quiet and stable.(3)Through the graded loading creep experiment on the rock with weak layer,and the acoustic emission signal during the rock creep process was also collected by acoustic emission equipment,it was found that the total creep of the rock with weak layer increased with the increase of the dip angle of the weak layer.A general trend;with the increase of the thickness of the weak layer,it shows a changing trend of "rising-stable-surge";with the increase of the number of layers,it increases linearly.The failure modes of rocks with weak layer dip angles of0° and 15° are mainly tensile splitting failure;the failure modes of rocks with weak layer dip angles of 30° and 45° are mainly shear slip failure;The rock always occurs sliding shear failure along the weak layer shear failure plane;when the number of weak layers is 1 and 2,the failure mode of the rock is mainly shear failure,and when the number of weak layers is 3,the rock failure The mode is tensile-shear composite failure.The acoustic emission spatial location results show that the acoustic emission source of the rock fracture process is mainly concentrated near the crack,and the acoustic emission events in other areas are less and the distribution is relatively scattered.(4)The continuous-discontinuous method(CDEM)was used to numerically simulate the whole process of creep failure of rocks with weak layers under constant load.This paper has 61 pictures,18 tables,and 74 references.