Theoretical And Experimental Research On Deformation Partition Of Axisymmetric Circular Roadway (Tunnel)

For a long time,the research of the deformation partition on the surrounding rock of soft rock tunnel(roadway)is always a relatively heated issue in domestic and abroad.For more than 90 years since the 1930s,hundreds of experts and scholars have been studying in this field from various aspects.Hundreds of papers have been published and a lot of achievements have been acquired in this period.Among them,several relatively representative ones are fennell calculation formula,theory of loose ring,three stage strain softening model,four stage strain softening model and so on.The obtained results have an important influence on the development of the support theory and technology of the tunnel.It is undeniable that the study of the topic is still at a developmental stage.Obviously,there are still some existing questions being discussing,which can be summarized in five aspects:(1)The "three-stage strain softening model" and "four stage strain softening model" as the basis of the zoning study did not take into account the creep property of rock.Instead,the peak compressive strength corresponding to the very fast loading situation is always as the peak stress of the model.The difference between the actual stress state of the surrounding rock and the rapid loading situation is ignored.The important objective fact that the rock has stable creep upper and lower threshold under sustained load is ignored.(2)It makes a variety of non-objective hypotheses to be formed that the variation of friction angle and cohesion force of plastic softening region rock is not clear while determining partition boundary.(3)The deep meaning of that the stress calculation formula of the plastic flow zone is not related to ground stress is not to be understood well.It is wrong to understand that the stress distribution in the region is not related to geostress as "the internal stress of the plastic flow area is independent of the ground stress".(4)The steady creep termination path line in surrounding rock has been ignored.(5)Some elements that need to be subjectively determined still exist in the analytical formula to determine the deformation partition boundary position.For the above problems,targeting the determination of deformation partitioning boundary and obtaining stress distribution in surrounding rock based on the creep property,comparatively deep theoretical and experimental study are made on the changing rule of internal friction angle and cohesion of surrounding rock of plastic softening phase,softening model of strain of surrounding rock and the distribution law of stress and displacement in each division,and finally,practical application of the paper's theory is presented in some detail by taking the battery-charging and rectifying room underground 848m in a 1000m-deep well(Panyi eastern Coal Mine)in Huainan mining district as research object.The important achievement of this paper includes following 7 aspects:(1)The views which rock internal friction angle changes little and rock cohesive force reduce sharply in the plastic softening phase are demonstrated.The views which the change trends of rock internal friction angle and cohesion should be consistent with rock strength are corrected.(2)The linear relationship between hoop stress and radial stress in plastic softening stage are obtained.At the same time,the nature of rock cohesive force softening modulus as a constant is revealed.(3)The surrounding rock stable creep upper and lower threshold are discovered.Four stages surrounding rock strain softening "new model" is created in accordance with the actual stress distribution of surrounding rock and the rock mechanics properties.(4)All kinds of partition type conditions are given.Each partition stress and displacement distribution law analysis formulas are deduced.(5)Combined with the peak compressive strength fitting line,stable creep upper and lower threshold fitting line and residual strength fitting line under different confining pressure,the analysis diagram about surrounding rock partition type and boundary stress is established.Using this diagram,the type of surrounding rock deformation partition and interface stress value can be simply determined by graphic method and analytic method.(6)The solution formulas and corresponding derivation process of each boundary stress and the boundary position are Systematic and comprehensive given.So,a good theoretical basis is provided for roadway supporting parameters(tunnel)quantitative design.For a wide variety of partition type and supporting intensity,the corresponding position in 4 stage of strain softening model of the stress in surrounding rock roadway inside edge is clear.The true quantitative research on the deformation mechanism of surrounding rock is realized.(7)The principle and method of 3 d in-situ stress test by sleeve crack puckering are given.The determination methods of surrounding rock partition type and each surrounding rock boundary stress and position are given by application.By the comparison of above results,measured results and numerical simulation results,the scientific and reliability of the theory and method in this paper are demonstrated.The research method of this article can be embodied in two basic characteristics.Firstly,it's the feature of the combination of theory and experiment.The whole article follows theoretical analysis,mixing with test research and supplementing with field application.The second characteristic is taking deformed and stable surrounding rock as research object in theory analysis,without considering the complex and fickle rheological process of surrounding rock.The involved parameters in the whole research are just two,the supra-threshold and infra-threshold of stable creep,which makes research ideas clearer and simplifies study process at the extreme.