| Large-diameter slurry shields are more and more widely used in tunnel construction,but their impact on the surrounding environment is more complicated,especially for deep soil deformation.Therefore,this paper relies on the large-diameter slurry shield construction project in the southern extension of Guangzhou Metro Line 4,through theoretical analysis and on-site measurement methods,studies the deep soil sinking deformation caused by large-diameter slurry shield construction.The main work and results are as follows:1.Using the soil deformation solution under the action of concentrated force,combining the additional thrust of the shield cutter head,the friction between the shield shell and the soil,and the grouting pressure of the shield tail,the calculation formula of the soil heave caused by the construction of the large-diameter slurry shield is obtained.In combination with actual engineering calculations and comparisons,it is found that the formula in this paper can better reflect the basic law of the overall heave of the soil,and the law of the influence of various construction parameters on the heave of the soil at different depths is also obtained,and the shield construction causes the main affected area of the overlying soil mass.2.Developed on-site measurement research programs including surface and deep soil mass sinking and uplifting,pore water pressure changes and other projects.Combining the incremental analysis method and the construction parameter data to the soil uplift data,it is found that the increase in the uplift of the deep soil caused by each construction parameter is greater than that of the ground surface,and the influence range of the shield tail synchronous grouting is compared with that of the mud sump.The pressure is wider and the influence is greater,and the shield tail grouting pressure is too large,which leads to the overall uplift,tilt uplift,and lateral uplift of the surface.3.Introduce the concept of heave difference,which is used to describe the degree of vertical separation and compression of soil,analyze the change process of heave difference of three onsite measured sections,and summarize five kinds of deep soil vertical separation And the compression deformation mode,combined with the construction parameters,it is found that the occurrence stages and causes of these five deformation modes are directly related to factors such as mud water tank pressure,shield tail grouting pressure,shield tail grouting volume,shield over-excavation,and formation loss.4.Based on the measured data,the grouting splitting and mud splitting caused by the largediameter mud water shield during the construction process are studied,and it is found that the excessive pressure of the shield tail grouting pressure and the mud water tank pressure will cause the soil to split and the shield tail The range of grouting splitting is the funnel-shaped range directly above the grouting hole.The angle between the boundary of the funnel and the horizontal line is about 25°.The maximum horizontal distance between the tip of the splitting crack is at least 7m.The range of muddy water splitting is concentrated on the top of the cutter head.In a small area of local soil,the length of splitting cracks is at least 1.5m.The splitting cracks of the shield tail grouting will continue to widen and extend due to the continuous increase of the grouting pressure of the subsequent working conditions.After the muddy splitting cracks are generated,they will be affected by the subsequent working conditions.The impact of the muddy water pressure is relatively small.Finally,this article summarizes and puts forward suggestions for shield construction to reduce soil splitting. |
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