Study On Supporting Technology Of Fluid Filling Lining In Deep High Ground Stress Soft Rock Tunnel

In recent years,the scale and depth of underground engineering in the nuclear industry,national defense industry,transportation and water conservancy industries have been growing at a high speed.Due to the complexity of geological conditions and deformation characteristics,the creeping time and deformation of deep high-stress surrounding rock can be up to 3 years,the creep variable is up to 1.6m,the support is too early,too late,and the lining stress is extremely uneven.A series of world technical problems that need to be solved urgently.In view of this,this paper proposes a deep high-stress soft rock tunnel fluid-filling lining support technology,which has the following four characteristics: 1 can give a certain amount of deformation space of the surrounding rock(30cm ~ 50cm);2 can be homogenized during the creep process of surrounding rock The lining is stressed;3 can provide the specified support force to the rock mass during the creep process of the surrounding rock,so that the final creep of the surrounding rock is greatly reduced;4reducing the overall construction cost.In order to quantitatively analyze the support effect and support mechanism of fluid-filled lining support technology,a series of tests were carried out.The specific research results are as follows:(1)Proposed the deep high-stress soft rock fluid filling lining support technology,the technology is divided into three stages: the initial stage of fluid filling lining,the equalizing pressure lowering stage than the pressure relief threshold,and the filling discharge pressure relief stage.(2)Study on the effect of different fluid fillings in non-leakage stage1)Independently researching the force-limited device under the non-venting condition of the fluid filling,carrying out the loading test under the condition that the fluid is not discharged,and obtaining the maximum deformation of the five kinds of fluid filling in the compaction process.The spatial order is 8mm soil>4mm soil>8mm low strength ceramsite>coarse sand>extra fine sand.2)Under the condition that the fluid is not leaked out,the five kinds of fluid fillings have better effect of reducing the peak load of the top layer of the buffer layer.When loading to the ultimate load,the load shedding effect of reducing the peak load of the top layer of the buffer layer is ordered as ultrafine sand(the peak load of the top of the bufferlayer is reduced to 49.29%)> coarse sand(reduced by 40.36%)> 8mm soil(reduced by25.20%)> 4mm soil(cut 17.43%)> 8mm low-strength ceramsite(12.3% reduction).3)Develop a fluid-filling and unloading effect device with adjustable lateral stiffness,and give the load-shedding law of filling ultra-fine sand,coarse sand and coarse-grained soil under different lateral stiffness of surrounding rock.(3)Research on lining support technology of smokable sand and engineering debris1)The smokable test shows that the deflection,bending moment and pressure growth rate of the mid-and 1/4 span are ranked as unbuffered lining > coarse sand lining > extra fine sand lining,indicating that the lining structure is stressed after the sand-filled buffer layer is installed.The bending moment of the larger position is greatly reduced with the increase rate of the load,the load shedding effect is remarkable,and the de-loading effect of the ultra-fine sand lining is better than that of the coarse sand lining.2)The trans-end deflection,bending moment and pressure growth rate are ranked as ultra-fine sand lining > coarse sand lining > no buffer lining,indicating that the sand-filled lining structure will equalize the load at the larger position to the position with less stress.And the fine sand lining is better than the coarse sand lining.3)Propose the waste soil and gravel with lower cost as the filling material,comprehensively consider the support,load shedding and fluid discharge effect,and give the optimal order as ultrafine sand> coarse sand> 8mm waste soil> gravel.(4)Visualization study of fluid-filled lining support technologyThe visualized loading and unloading device was developed,and the space-time evolution law of the fluid leakage cavity area and the corresponding unloading effect were established.The technical method for determining the development of the fluid cavity leakage cavity area was given.(5)Study on isolation and impact resistance of sand and engineering debris lining1)For the lining support of sand and engineering waste debris,the law of removing vibration and impact load under different fluid filling thickness is given,and finally the method for determining the optimum fluid filling thickness for determining the complete unloading vibration and impact load is given.2)The variation law of impact stress with settlement at any moment in the impact process is given,and the relationship between impact stress and velocity,time and settlement is established.(6)Engineering application researchBased on the numerical simulation analysis of the Danba project,the traditional support and the fluid filling support force were compared and analyzed to verify the feasibility of the fluid-filled lining support technology.And summarize the effects of different fluid filling lining support technology,give the material characteristics of fluid filling material and material cost comparison table,provide reference for practical engineering.