Study On The Influence Of High Pressure Rotary Jet Grouting Secant Pile Bottom Reinforcement On Granitic Layer On Pit Deformation

Guangzhou metro station has many sites whose geological condition is complex,many of which are built in the formation of granite, for example Yuexiu park stationof metro line2, Yantang station and Plum garden station of north delay section inmetro line3, Xinzao station of metro line4and Tianpingjia station of metro line6are all built on the granite layer with complex engineering properties. Excavation inbad granite formation directly, causes deformation of foundation pit is often larger,for example the deformation of underground continuous wall of the Plum gardensubway station foundation pit under construction process is up to10cm, which hadcertain adverse effect on the foundation pit. Although the understanding of theengineering properties of granite layer has greatly improved, but an economic,reasonable, scientific and sufficient method to deal with it effectively has not found.The article takes study of the influence to the pit deformation due to highpressure jet grouting pile in the reinforcement granite layer as follows, combiningwith the station foundation pit construction and the monitoring items of Guangzhourail transit line6.(1) This paper summarizes the mechanism of the deformation of foundationpit, discusses the main influencing factors of the pit deformation, and explain thecalculated foundation settlement uncoordinated situation using the compressionmodulus method and deformation modulus method for composite foundation designwith the residual soil, then pointes out the calculated result using two methods is safe.Relative to the compression modulus method, using the deformation modulusmethod to calculate settlement of foundation is more reasonable. The effect on thedeformation mechanism due to soil consolidation in the passive area is analyzed.(2) The geological data and experimental data of Tianpingjia station areanalyzed, and the strengthening regularity of deformation conditions is concluded.(3) This paper takes Guangzhou rail transit line6Tianpingjia station foundationpit project as the background, focus is the analysis of the rule of the effect on thedeformation of inner supporting underground continuous wall from high pressure jet grouting pile foundation treatment in granite layer based on the field data. First,analyzing the deformation mechanism of the effect on pit deformation due to soilconsolidation in the passive area, simulating the Tianpingjia station foundation pitengineering using finite element software, comparing the simulation results with themeasured data analysis, verify the feasibility of the software on the analysis of theseproblems, analyzing the simulation curve. Then in order to illustrate the foundationtreatment effect, the simulation results are compared with the simulation result ofunderground continuous wall which do not make foundation treatment.(4) In view of the Tianpingjia station foundation pit engineering, in order tooptimize the design and construction, this paper do study on the reasonablearrangement of the high pressure jet grouting occlusion pile. Finally, the effect onfoundation pit deformation by the thickness and embedded depth of the continuouswall under the condition of the occlusion pile foundation treatment is studied.