Research On Rheological Properties Of Weak Cemented Soft Rock And Roadway Support Technology

In all kinds of rock mass engineering,such as foundation of earth and rock dam,soft rock mass of slope,tunnel,roadway,subway station and so on,the stress and strain in underground tunnel engineering changes constantly with time,showing remarkable rheological characteristics.Western China mine construction process often encounter the Jurassic and cretaceous soft rock stratum.This kind of stratum rock has such problems as low strength,poor cementation and easy to disintegrate and sloughing under water,and has remarkable rheological deformation characteristics under long-term external load,which brings adverse effects to the mine construction and reduces the service life and service level of underground structures such as underground chamber and roadway.The soft rock roadways in Hongqingliang Mine were taken as the research object.The indoor experiment,theoretical analysis,numerical simulation and theoretical model calculation method was adopted.The physical and mechanical properties tests was carried out by using TAW-2000 type rock triaxial apparatus under different loading rate and water cut under the condition of uniaxial compression test and triaxial shear test,based on the theory of fractional calculus weakly consolidated soft rock creep constitutive equation.The creep property test of weakly consolidated soft rock was carried out by using the GDSTAS soft rock rheological triaxial instrument to increase the grade of confining axial pressure and the grade unloading of confining confining pressure.By using MIDAS/GTS to establish the numerical calculation model of weakly cemented soft rock roadway,the plastic zone,surface convergence deformation and stress distribution of surrounding rock under different support schemes were compared and analyzed,and the support scheme for rheological characteristics of weakly cemented soft rock was proposed.Through research,this paper got the following results are as follows:(1)The physical and mechanical properties of weak cemented soft rock in Hongqingliang Coal Mine were tested,and the density and water content of rock samples were measured by laboratory tests;the structure of soft rock softened by weak cementation in water was given by polarizing microscope,high power microscope and scanning electron microscope,and the composition of the rock was measured by X-ray diffraction analysis.(2)The uniaxial compression test of weak cemented soft rock is carried out by using TAW-2000 rock triaxial testing machine.The test results show that the uniaxial test curves of weak cemented soft rock include compaction stage,linear elastic stage and peak strength after elastic-plastic stage.At the initial stage of loading,the axial strain-stress curves and uniaxial curves of the specimens under the condition of constant-rate stress loading mainly undergo axial compression deformation.At the later stage of elastic deformation,the radial expansion strain of the specimens gradually increases,the volume expansion of the specimens occurs,and the lateral expansion deformation mainly manifests as lateral bulge deformation.Based on Mohr-Coulumb criterion,the shear strength envelope of weak cemented soft rock under triaxial test is drawn.(3)Based on Riemann-Liouville fractional calculus operator,the Abel clay pot is introduced.The attenuation creep,constant velocity creep and accelerated creep of geotechnical materials are reasonably described by fractional order number beta in the Abel clay pot.Several common fractional calculus element models and their numerical solutions are given.The four-element model of H-body-Abel-C | Abel clay pot is proposed to simulate creep characteristics of weak cemented soft rock basing on the fractional-order Burgers Model.(4)Triaxial creep test of weakly cemented soft rock is carried out by using GDS-HPTAS triaxial creep tester,and two creep test loading schemes,i.e.rising and unloading confining pressures,are proposed to study the variation characteristics of axial and radial creep curves,axial and radial creep rate curves of weakly cemented soft rock under different creep loading conditions;the length of weakly cemented soft rock under different water-bearing conditions is obtained by using isochronal stress-strain curve method.Three steady-state creep parameters,Em??1 and ?1,and five non-steady-state creep parameters are calculated by using the function of mathematical regression analysis in origin.The creep properties of weak cemented soft rock are increased by ?2 and ?2.The variation of model parameters with experimental conditions is given.The creep test results under two test conditions are verified and analyzed.(5)The KDZ1114-3 portable mine geological detector is used to predict the fault strike,tendency and drop of the return air roadway of No.3-1 coal in Hongqingliang Coal Mine;the finite element software MIDAS/GTS is used to establish the numerical calculation model of weak cemented soft rock roadway crossing the fault fracture zone,and the distribution characteristics of surrounding rock plasticity,maximum stress(variation)and bolt(cable),shotcrete and grouting bolt(cable)are analyzed.The mechanical characteristics of supporting structures such as steel brackets are analyzed,and the parameters of bolt support are calculated based on the theory of.In the area affected by fault fracture zone,corresponding stations are set up to monitor the convergence deformation of surrounding rock,the stress of bolt(cable),roof separation and the stress of bolt.The applicability of bolt-mesh-cable-shotcrete combined support in soft rock roadway crossing fault fractured zone is verified.The above research results will provide a scientific basis for the design of weak cemented soft rock underground engineering in Western China,and promote the development of rock rheology,underground structure design theory and other disciplines.This paper has 139 figures,25 tables and 121 references.