Study On The Bottom Stress And Deformation Characteristics And Settlement Control Of Soft Loess Tunnel

The bottom stress and deformation characteristics of soft loess tunnel have been concerned byacademic and engineering. Due to the particularity of loess engineering properties, the tunnel bottom stressdeformation characteristics of loess tunnel are different from mountain tunnel. In order to clarify thedeformation characteristics of soft loess tunnel bottom and put forward effective settlement controlmeasures. This paper take the Da You Shan loess tunnel project as the research object, analysised the tunnelsurrounding rock stress distribution and deformation, tunnel bottom reinforcement and settlement control,combined with numerical simulation and field measurement methods. The main conclusions are as follows:1. Simulated two kinds of working conditions of loess tunnel step construction process, analyzedtunnel surrounding rock stress distribution and deformation laws combined with the field measured data.The results show that the surrounding rock stress distribution is not uniform in the inverted arch area, stressis larger in the sidewall Angle with inverted arch, while it is smaller in the inverted arch center and theuplift of tunnel bottom is obviously. The tunnel bottom soil stress decreases, the plastic zone anddeformation are increased under the influence of the rain.2. Compared and analyzed some commonly used treatment measures of soft loess tunnel bottomreinforcement. We can see that high pressure jet grouting pile method have the advantages of lessconstruction covers area, small vibration and better reinforce quality. And suitable in the bottomreinforcement of Da You Shan loess tunnel.3. Analyzed the composite foundation formed by high pressure jet grouting pile, Studied on the bottomdeformation and stress characteristics of loess tunnel, we can kNow that the tunnel convergence is mainlylocated in the side wall after foundation treatment, the tunnel bottom uplift significantly reduced, and theplastic zone is mainly distributed in the upper part of the tunnel.4. Simulated the post-construction settlement of the tunnel, and comparatived with the fieldmonitoring results. The results show that tunnel subsidence deformation mainly occurs within12days afterthe inverted arch completion backfilled, then the deformation rate decreases, and deformation basicallystable at the36day.