| Because of its advantages of environmental protection,high utilization rate of section and strong adaptability of shallow soil,the large section rectangular pipe jacking method is an efficient green trenchless technology for driving through urban roads,rivers and subway entrances and exits.However,there are some problems in the construction safety and the disturbance control of the working face soil in the long-distance and large cross-section rectangular pipe jacking tunnel project,which seriously restricts the application of the non excavation technology of rectangular pipe jacking in the river crossing tunnel project.In this paper,based on the background of Suzhou shallow soil large section rectangular pipe jacking through the Beijing Hangzhou Grand Canal tunnel project,the characteristics and influencing factors of soil disturbance and deformation in large section rectangular pipe jacking construction are analyzed by means of field investigation,theoretical analysis,numerical simulation and other research methods,the law of soil disturbance evolution in large section rectangular pipe jacking construction is revealed,and the large section rectangular pipe jacking through Beijing Hangzhou Grand Canal tunnel is proposed Soil disturbance control technology and monitoring scheme of the Grand Canal.The main research results are as follows:(1)This paper analyzes the disturbed deformation characteristics of soil mass during the jacking operation of rectangular pipe jacking under the time effect,and analyzes the mechanical effect and stress division of the soil around the pipe.Combined with the engineering characteristics and difficulties,the main influencing factors of the disturbed deformation of the soil mass in the project of large section rectangular pipe jacking under the Beijing Hangzhou Grand Canal are analyzed.(2)It is determined that the best grouting pressure of the project should becontrolled at 180 kPa,about 1.1 ~ 1.2 times of the gravity of the overlying soil,and the grouting control effect is the best.With the increase of grouting pressure,the settlement of soil at the upper part and the rebound of soil at the bottom of the tunnel decrease nonlinearly,while the deformation of pipe joint and soil at both sides increases nonlinearly.When thkPa,the average subsidence rate of thesurface is 0.08mm/kPa,and when thkPa hkPa,the average subsidencerate is 0.02mm/kPa.(3)The total jacking force predicted by the formula considering the average friction is P h kN,which needs to be supplemented by the intermediateforce,and the disturbed deformation law of soil layer under different jacking forces is obtained.Considering that the total jacking force predicted by the formula of average friction resistance is P h kN,which is greater than the reaction force ofbackseat,the relay room needs to be set;when the jacking force of this project is 1P(P is the vertical pressure of soil in the center of the working face),the soil disturbance is the smallest,and most of the vertical deformation of the ground surface is completed within the axial range of 2.9D(D is the rectangular jacking span).The horizontal settlement area of the surface is basically the same with different jacking force,about tP D.(4)This paper studies the mechanical characteristics of the large section rectangular pipe jacking under the Beijing Hangzhou Grand Canal,reveals the vertical,horizontal and axial deformation laws of the soil mass,expounds the rationality of the values of the jacking force and grouting pressure in this paper,and the necessity of the surface settlement control technology and monitoring scheme of the river crossing section.The nearer the working face is,the faster the decrease speed of intransverse and axial direction is,and the influence area is concentrated in the rectangular excavation area within 1.2D in front of the working face.After excavation,the vertical stress distribution in the overlying soil is “U”.After the pipe jacking crossing the Beijing Hangzhou Grand Canal,the surface subsidence increases by 70%compared with that before the river crossing.The maximum surface subsidence of the whole top section is about 29.51 mm,which is different from the distance between the working face and the horizontal monitoring face.The closer to the working face,the larger the lateral horizontal deformation of the soil on both sides of the tunnel,the outward expansion of the lateral compression area as a circular surface,the smaller the outward deformation of the soil on both sides away from the working face,the farther away from the working face,the closer the lateral displacement of the soil to the pipe joint.The axial displacement of the soil layer is the largest in the jacking direction in front of the machine head,and the maximum displacement of the soil at the interface of the machine and the pipe from the jacking direction.(5)The vertical deformation of the earth's surface predicted by Peck and cumulative probability curve is studied.The calculation shows that the lateral influence range of land subsidence is(-30 m ~ 30m),and the maximum subsidence is33 mm.The trend of surface transverse settlement is “U”.The law of axial surface settlement is basically the same as that of numerical simulation.(6)The control technology and monitoring scheme of the surface deformation and the disturbance of the shallow buried River soil are put forward.There are 63 figures,5 tables and 122 references in this paper. |
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