Research On Deformation Control Of Ground And Excavation Face For Pipe-jacking

The pipe-jacking construction technology is favored in the transformation and urban pipelines for its advantages of non-excavation and high safety.However,ground deformation and excavation face collapse are caused by improper process and geological conditions in construction,which will not only lead to detrimental effect on surroundings,but also influence the smooth running of pipe-jacking.The rational control of deformation of the ground and excavation surface is the key to solving above problems.In this paper,combined with the actual practice of pipe-jacking project in Zhengzhou,considering the progressive process and lateral friction of pipe jacking,the following contents are researched:(1)In theory,the essence of ground and excavation surface deformation caused by soil stress release during pipe jacking is discussed.Additional stress produced by grouting,friction and supporting,are taken into consideration separately to study the soil deformation trend in the excavation area and the mechanism in disturbance area.(2)The essence of soil excavation in pipe-jacking is studied from the perspective of stress release by numerical simulation,the relationship between soil deformation,mechanical change and stress release rate during steps is obtained;The pipe joints jacking process is simulated by the displacement control method,friction between pipe and soil is also considered.The law of ground deformation under different working conditions are studied;regard the pressure effect of grouting as the loading process of the soil,different grouting pressures are simulated by nodes stress controlling to study the influence of ground deformation;(3)Based on the numerical simulation method,through the amplitude curve to control the supporting pressure,the process and trend of the excavation face deformation during the change of supporting pressure and the additional surface displacement caused by instability process are studied.The failure modes of excavation face under different depths of burial,different friction angles,and different cohesive are also discussed;(4)Combined with pipe-jacking project in Zhengzhou,corresponding monitoring points are placed at different locations on the ground,the collected data are compared with the ground deformation trend from simulation results to verify the rationality in trend analysis by numerical simulation method.