| Alteration rock is a familiar special rock mass at the district of Lingnan, the difficultly controlled large deformation of surrounding rock and water gushing and sudden mud usually occur when a tunnel passes the distribution area of alteration rock due to its complex distribution, water-riched and special mechanical property. Taking the two typical construction sites of the newly constructed Luo-zhan railway as examples, in this paper the research means of field survey, the experiments in the laboratory, theory analysis numerical computation and model test are comprehensive used. The mechanism of the tunnel’s large deformation and the control measurements for the construction in the alteration strip of granite containing rich water are deeply studied.(1)On the basis of survey and analysis, the space-time distribution rule of alteration rock and the engineering geological condition at the typical work site are concluded; the indoor and outdoor experiment are carried out, the mineral ingredient and physical and mechanical property are analyzed, stress-strain relation is also discussed, the deformation characteristic of alteration rock is established. Engineering geological characteristic of the surrounding rock alteration rock is concluded which becomes the test basis for further deformation mechanism analysis.(2)By construction deformation inversion, constitutive model according with altered rock’s deformation features is put forward. That’s damage model or ss softening constitutive model.So reasonable explanation for large deformations of surrounding rocks mechanism is obtained. The calculation model of generalized complex rock mass structure is built up and numerical computation is carried out, tunnel’s deformation convergence characteristic is analysed at different positions relation among tunnel, altered rock and sedimentary rock.(3)Two kinds of control measurements for the construction of the large deformation are put forward as well as be taken into practice.First, the point safety statement of surrounding rock different positions are considered, excavation loose region of zone analysis method based on point safety factor field is employed. Second the dynamic design method is adopted, through the experience and monitoring and analysis of surrounding rock convergence displacement development rule, the surrounding rock deformation characteristics are determined as well as the single-time strong support method to control the latent large deformation of surrounding rock.(4) Based on fluid-solid coupling theory, strength reduction FEM widely used in the calculation of slope stability is introduced into the excavation face stability analysis, based on the safety coefficient to quantitative evaluation of the excavation face stability, deformation mechanism and control measures of the alteration rock’s tunnel under the seepage condition are studied. The range of loose region in front of the excavation face is obtained as well as the principle of water control methods which should be carried out in the process of excavation, the reinforcement scope of tunnel perimeter and advanced pre-grouting is also determined.(5) By the size ratio model test, the correctness of the preceding chapters related theoretical analysis and actual conditions of construction field are well corroborated... |
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