| The shield construction of tunnel engineering in typical sand layer was taken as the background in this paper.With the consideration of factors such as the pipeline number,pipeline type and depth,space position of pipeline-tunnel and pipeline spacing,model test and theoretical analysis were applied to study the influence of tunnel construction on the adjacent buried multi-pipelines in sand.The main research contents and conclusions are as follows.(1)In order to study the influence of tunnel construction on the adjacent buried multi-pipelines in sand,the indoor model test was designed,and the feasibility test was demonstrated.The test procedure,precautions and measurement scheme of model test were elaborated.(2)In order to study the influence law of vertical tunnel penetration on adjacent buried pipelines,indoor model tests of different pipeline numbers,pipeline types,pipeline depths and pipeline spacings were carried out.The results showed that the settlement curve of single pipeline was consistent with the characteristics of Gaussian curve.Pipelines with less rigidity was better adjusted to the soil deformation,and the settlement was larger.When the ratio of pipeline to tunnel depth z/h was in the range of 1/4?3/8,the maximum settlement of the pipeline was greatly affected by the pipeline depth.Compared with the situation of single pipeline,the overall deformation of multi-pipelines was consistent with that of single pipeline,and the pipeline spacing had larger effect than the pipeline type on the maximum settlement.Through statistical analysis,the calculation method of pipeline settlement,regarding to pipeline spacing,was proposed.In the relative stiffness theory of pipeline-soil,the width ratio of the upper arch zone to the pull-down zone was linear with the pipe spacing.The results of the research on the pipeline stress and the soil pressure at pipeline bottom showed that the positive bending moment of the pipeline was located at the midpoint of the pipeline,and the negative bending moments were 1.5D from the tunnel axis on both sides.The maximum restraining forces of the soil on the pipeline were 1D from the tunnel axis on both sides.(3)In order to study the influence of parallel pipeline-tunnel position on adjacent multi-pipelines,the tests of different different pipeline depths and pipeline spacings were carried out.The results showed that the deformations regularity of settlement on both sides of tunnel excavation surface were consistent as a whole.The pipeline settlement curve gradually advanced in similar linetype,and finally was stable at a certain.The pipeline buried depth had little effect on pipeline settlement.The influence of the pipeline spacing on the final settlement value was the same as that of the vertical pipeline-tunnel position.(4)Based on the principle of minimum potential energy,the variational governing equations was established by the energy method.Together with the theoretical calculation of MATLAB,the method of calculating the vertical settlement of signal pipeline caused by the vertical underpass tunnel was obtained,which was verified by the example.On the basis of the energy variation method,considering the pipeline spacing,the modified energy variation method and the internal force calculation method of pipeline were proposed,and it was verified with examples,whose results were great.The influence of soil property,buried depth,stiffness,and ground loss rate on the settlement caused by tunnel construction was analyzed.The results showed that the ground loss rate had the greatest influence on pipeline settlement.Based on the energy variational method,a calculation method for pipeline internal force caused by the vertical tunneling of the pipeline was proposed. |
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