Research On The Ground Settlement Law Of Pipe Jacking Construction With Pebble Soil

The pipe jacking method is a non-excavation construction process,which has great advantages compared with the open cut method in underground pipeline laying and tunnel excavation.However,after the pipe jacking method is excavated underground,it is inevitable that the soil layer will be disturbed and deformed.The resulting soil loss will induce holes and collapses in the stratum,which will endanger the safety of the project and personnel.Therefore,it is necessary to carry out accurate analysis and calculation of the formation deformation caused by the pipe jacking method for underground pipelines.Based on the actual background of pipe jacking engineering,this paper studies the settlement problem caused by the pipe jacking method.The main work contents and research results are as follows:(1)Based on high-density electric exploration technology,the stratum of the construction area is surveyed,and the geological survey data is combined to obtain the distribution of gravel in the stratum of the construction area.The pipe jacking construction is guided to avoid the dense gravel area,pay attention to the gravel stratum.The excavation method reduces the influence of construction on the ground disturbance,thereby reducing the settlement deformation caused by the construction.(2)Based on the mature theory of tunnel shield mechanism construction to stratum disturbance mechanism,the stratum disturbance mechanism caused by pipe jacking construction is analyzed,and the main factors affecting settlement and the characteristics of time and space effect of stratum settlement are given.(3)Analyze the monitoring results of surface subsidence,and use the ground penetrating radar technology to detect the hidden dangers of the pipe jacking construction,mainly based on monitoring and testing.The monitoring results show that the pipe jacking construction has little effect on the stratum disturbance,the settlement value meets the allowable value of the standard,and the settlement law accords with the theoretical analysis of the disturbance mechanism.The radar test results show that no obvious hidden dangers such as cavities and collapses are found,and the overall quality of the project construction is better.it is good.(4)Based on the Peck formula,the mathematical ground regression method is used to fit the measured surface settlement data,and the key parameters in the Peck formula are corrected according to the fitting result.The corrected soil loss rate is 2.6%~3.7%,the recommended value of the project in this area is 3.3%;the value of the settlement coefficient of the settlement tank is 0.58~0.75,and the recommended value of the project in this area is 0.66.(5)Numerical simulation analysis of surface settlement caused by pipeline excavation based on finite difference method software FLAC3 D is carried out.The numerical simulation results are in good agreement with the actual measurements.The displacement laws of the soil below the surface and the key parameters affecting the formation settlement are analyzed.It is concluded that under certain conditions of the project,the smaller pipe diameter,shallower buried depth and tamping reinforcement of the soil layer can be used to improve the elastic modulus of the soil,which can effectively reduce the disturbance of the stratum by the pipe jacking construction degree.