Study On The Triaxial Mechanical Properties Of Weak Swelling Soft Rock

Through laboratory experiments of gray mudstone from Guyuan area,obtainedthe swelling properties,the mechanical parameters and stress-strain curves. Analysisedof the changes in the parameters of gray mudstone in detail.On the basis of classicalconstitutive relations,put forward the constitutive relation suitable for the mudstone inthis region. Using FLAC3D numerical software,simulated the gray mudstone tunnelexcavation and support programs.The details are as follows:(1) The gray mudstone from Guyuan area are mainly composed of clay mineral andcalcite.In the statistical analyses, the gray mudstone from Guyuan area is weakswelling soft rock.In the water-saturated state,the mechanical parameter of graymudstone such as compressive strength and elastic modulus reduced very significantcompared to natural state.Strength of the gray mudstone increases with confiningpressure.It is more apparent in the water-saturated state.(2) By analysis of micro-fracture compaction stage,this stage of the axialdeformation was divided into two parts.The first deformation be caused by themicro-cracks was pressure-tight, and the second be caused by the properties of themudstone Sample.The compaction paragraph of elastic potential energy can bedivided into two parts too. The first elastic potential energy be caused by themicro-cracks was pressure-tight, and the second be caused by the properties of themudstone Sample. Defined the energy crack density was the ratio of the former withthe latter. On this basis, build relations between the peak strength and the energy crackdensity.Energy crack density decreased with the increase of confining pressure.Increase of confining pressure can reduced the influence of micro cracks to the peakstrength. In a certain extent,this article has been the quantitative analysis, and definedthe impact of micro cracks to the peak strength.(3) The improved Five sections of the linear constitutive relations,it not only takeninto account the strain softening of rock specimen, also increased the micro-fracturecompaction stage.It was a good simulation of the rock pressure section, elastic stage,strain hardening stage and strain softening stage, residual plastic stage.The fivesections of nonlinear constitutive relation model,it absorbed the advantage of theDuncan model in the simulation of the rock elastic stage and strain hardening stage, atthe same time increased the constitutive relation of pressure section, strain softeningstage and residual plastic stage.It’s closer to the actual reality of a rock constitutive.(4) Under the condition of excavation and anchor spray support,did the numericalsimulation of soft-rock tunnel.After anchor spray support,the plastic deformation zoneand displacement of rock decrease obviously;the stability of soft-rock tunnel havegreatly improved;the effect of support measures was obvious.Did the orthogonalexperiments and for different anchor spacing and different anchor length, and thenumerical calculation for the different support schemes.Through the analysis of the deformation of tunnel surrounding rock and the stress changes, choose the mostreasonable supporting scheme.