| The status quo of China’s coal resources as the main source of energy can not be changed in a short period of time, the mining depth of coal increased year by year, the application of deep mine inclined- shaft will be more and more. In order to improve the construction efficiency, TBM(shield) will be imperative for inclined-shaft construction. But study of the stress characteristic and stability of the inclined-shaft lining structure constructed by TBM(shield) is not mature, and related research results are less.In this paper, according to the engineering geological data, supporting structure design and construction method of Shenhua Taigemiao mine inclined-shaft of TBM construction, many sciences are made full use to arrive mechanical characteristic of surrounding rock and supporting.The used sciences are as follows: the elastic- plasticity theory, tunnel mechanics, rock mechanics, structural mechanics, mine geology etc. The analytical solutions of displacement, stress and strain of the surrounding rock, segment lining structure and bolt-shotcrete support structure are derived. Several construction processes are simulated by FLAC3 D software. The internal forces of segment supporting structure under non-uniform loads are calculated by the finite element software ANSYS. Main works are as follows:1. Theoretical analysis and numerical calculation of spatial effect of excavation face during excavation without support.(1) The deformation of soft rock is not instantaneous, that means it needs enough time for surrounding rock to finish final deformation. At first, The existing formulas are used to calculate displacement and stress of the surrounding rock of every excavation step. The effect laws of the spatial effect of excavation face on them is obtained in the process of advancing of the shield tunnel face.(2) The FLAC3 D software is used to simulate the whole excavation process. supporting process is not considered now. The range of excavation is 59.5m long, and each excavation distance is selected as 1.5m.The displacement and stress of the surrounding rock of each excavation step is extracted. Their change laws with excavation step is concluded.(3) The comparison of analytical solution and numerical solution of the surrounding rock displacement reveals that the law of development of them with tunnel face advancing are consistent. Displacement of the observation surface begins to increase from zero when the tunnel face is 2 times radius of tunnel before the observation surface, until it is 5 times of the radius of tunnel after the observation. The depth of tunnel is more large, the release of surrounding rock displacement is more slowly. So it needs to more time to achieve stable state.(4) According to the comparative analysis of the analytical solution and the numerical solution of the surrounding rock stress, the main stress variation features of them are the same.The radial stress reduces and the tangential stress increases greatly after excavation. The analytical solution and the numerical solution have one difference.The analytical solutions of the radial stress and the tangential stress remain unchanged before or after excavation, but they have a transient change after excavation. The numerical solutions are more in line with the actual endineering. This is caused by neglect of effect of the spatial effect of excavation face.2. Theoretical analysis and numerical calculation of mechanical characteristic of bolt- shotcrete support in shield construction process.(1) Through the theoretical calculation, the earliest support times for For bolt-shotcrete support type according to the four depths of 300 m, 400 m, 500 m and 600 m are respectively determined as follows: 2.5, 2.56, 2.98 and 3.34 times the radius. The conclusion is arrived that the section of a greater depth needs a later support time.(2) The analytic solution of stress of the anchor support structure in the construction process is calculated. And the comparative analysis of stress development process of several different support times of the anchor- shotcrete support structure is made. For a certain depth of tunnel, supporting more later, and surrounding rock pressure is more smaller. The stress of lining structure will benefit from later support, but if supporting is too late, support will be against the surrounding rock.(3) The excavation and anchor- shotcrete support process are simulated with FLAC3 D software, and the numerical calculations of the displacement and stress of the anchor- shotcrete support structure are calculated. The change laws of them are found out. Than it is comparised with the surrounding rock displacement during excavation process without support.get the anchor-shotcrete support structure hardly affect the deformation of surrounding rock in construction, and only reduces the displacement speed.(4) The constructions of excavation and anchor- shotcrete support according to several different supporting times are simulated with FLAC3 D software. And the numerical calculations of the displacement and stress of them are calculated. Then the change laws of the displacement and stress with the support time are found out. The values of the ultimate displacement and stress are extracted. The effect laws of the support time on them are analysed.(5) Four different lateral pressure coefficients are assumed, then the numerical calculations of the displacement of the bolt- shotcrete support structure and the pressure of the surrounding rock are arrived through the numerical calculation of the excavation and support process of 500 m deep tunnel with FLAC3 D software one by one. The effect laws of lateral pressure coefficients on their change process with tunnel face advancing are analysed. The influence degrees of the lateral pressure coefficient and supporting time are comparised, and it shows that the influence of supporting time is significant.3. Theoretical analysis and numerical calculation of mechanical characteristic of segments support structures in shield construction process.(1) Based on the spatial effect of tunnel face, the mechanical model of the segments lining structure is established with backfill layer considered. The analytical expressions of stress and strain of the segments lining structure and the backfill layer in the excavation and support process are derived. The analytical sulutions of pressure on the support structure in the process of tunnel face advancing. The analytical solutions of stress of the segments lining structure and the backfill layer. The change laws of the stress in the excavation process of TBM(shield).(2) When the spatial effect of tunnel face is considered, the excavation of TBM(shield) and support process of segments are simulated with FLAC3 D software. The values of the stress of the segments and the backfill layer are extracted. The change laws of them with the tunnel face advancing are analysed.(3) Four different lateral pressure coefficients are assumed, then the numerical calculations of the displacement of the segments support structure and the pressure of the surrounding rock are arrived through the numerical calculation of the excavation and support process of 500 m deep tunnel with FLAC3 D software one by one. The effect laws of lateral pressure coefficients on their change process with tunnel face advancing are analysed. Then the lateral pressure coefficient influence degrees and the support time are comparised, and it shows that the influence of supporting time is significant.(4) According to the comparative analysis of the analytical solution and the numerical solution of the segments stress and the backfill layer, the stress change laws of them with construction process are the same. But the numerical solution of the stress gets stable earlier.4. Theoretical analyses of effect of backfill layer on the segments lining structure(1) The stress of segments lining structure is calculated with elastic mechanics when the backfill lsyer is egnored. The values are compared with the ones when the backfill layer is considered. According to the analysis of the backfill layer on the stress of the segments lining structure, it can make the absolute values of the stress of the segment lining structure decrease a lot. Advice is given that reduction of the surrounding rock pressure should be made to cut costs in actual design.(2) The backfill layer is a composite material consisting of pea gravel and cement mortar. The homogenization theory, the perturbation technique and the theory of elastic mechanics are used to propose new method of duducing the analytic expression of the equivalent elastic modulu of the Compound material. The analytical expressions are derived. With the new method, the equivalent elastic modulu of the backfill layer in Shenhua Taigemiao mine inclined-shaft of TBM construction is calculated. The Hook,s law is used to calculate the strain of the the segments lining structure based the stress of derived above in the paper. The comparision of strain of the segment lining structure with backfill layer and not considered.The conclusion reveals that the backfill layer is good to stability of the segment lining structure.(3) In TBM construction, the pea gravel is filled around the segment lining structure behind the shield tail, and then the cement mortar is grouted immediately. The strength of the cement mortar changes along time within 28 days. The side friction resistance on the segment lining structure changes. According to a large number of literatures and specifications, shear strength curves of pea gravel backfill layer in different period of time are fitting out, the expression of the maximum friction on the side lining can provide at all stages is derived.(4) In TBM construction process, shield machine thrust jacks is support on the segment lining structure. The reverse thrust on the thrust jacks is supplied. At the same time, the thrust on the segment rings is produced. Mechanical characteristics of all segment rings are analysed with the calculation formula of side surface friction of segment lining In every period of time. The interaction between rings is analysed. he effect range of the reverse thrust of in the construction process.the change rules of segment ring pressure force and the lateral surface shear stress within the scope of influence are studied.5.Mechanical characteristic analysis of segment lining structure under non-uniform loadings.Non-uniform loads often appear in the coal mine engineering. Deformation of segments under a non-uniform load is calculated for a common load distribution pattern. After consulting a lot of literatures, comprehensive analysis is done to determine the elastic resistance coefficient of the surrounding rock. According to the lining deformation and the elastic resistance coefficient of the surrounding rock, the distribution pattern of the elastic resistance caused by the non-uniform load is determained. The equation of inner forces of the hinged ring model under the non-uniform load and resistance was solved. Based on the engineering background of this paper, the analytical method is used to calculate the analytical values of the bending moment and the axial force of the segments, and the surrounding rock and lining system are numerical simulated with ANSYS finite element software. In the finite element simulation, the freedom degree of the beam188 unit is released to think of joints as no moment transfer. The numerical solution of the modle considering and the analytical solution of the homogeneous ring model are compared. The same points and the differences of inner forces distribution of the two models are obtained and some suggestions are put forward. |
