| As a comprehensive urban resource transportation system,underground comprehensive pipe corridor not only brings convenience to the life of urban residents,but also has hidden safety risks that cannot be ignored.In this paper,the underground pipe corridor of the west coast new district of Qingdao city is taken as the engineering background.The mechanical analysis of the pipe corridor excavation under the condition of overlaying rock thickness of 2-3m and horizontal distance of 0.5m is carried out by using the numerical simulation software,and the optimal plane design of the underground comprehensive pipe corridor is determined.A total of 12 working conditions are studied,and three pre-selected schemes are selected.The analytic hierarchy process was used to analyze the construction risk of underground comprehensive pipe corridor,and the optimal solution was selected from three pre-selected schemes,namely,the minimum risk of overburden thickness and safety distance,which could reduce the probability of the occurrence of underground pipe corridor risk.The core risks mainly include corridor structure safety,pipeline safety,internal environment,external environment,facility safety and man-made damage.The main research results of this paper are as follows:(1)This paper refer to specification to sort out the characteristics of the current comprehensive utility tunnel,space design and overall planning,combined with the west coast of Qingdao city new district underground utility tunnel geological conditions,construction and design,in the space design according to the existing standard to calculate the pipe rack and optimum spacing of existing pipeline could range between 3 m to 4.7 m.(2)FLAC3D numerical simulation software was used to establish numerical simulation analysis for 12 different working conditions in a range of 2～3m.The results show that the internal stress of soil decreases in a wave mode during excavation and becomes stable after reaching the critical point.After excavation,the original stress state of soil mass was destroyed,and the soil mass around the foundation pit was loosened.The distribution rule of pipe stress was>on the lower side and>on the upper side,and the pipe wall stress decreased with the decrease of horizontal distance.The influence of soil mass on the displacement of pipeline increases with the decrease of horizontal distance of excavation,and the maximum displacement area moves to the lower right along the lining.As the thickness of the overburden increases,the stress on the pipe wall increases first and then decreases at the same horizontal distance.The distribution of the stress on each quadrant point is also different,showing a nonlinear law.According to the correlation degree,three optimization schemes are preliminarily determined.(3)The evaluation system is established by means of analytic hierarchy process.On this basis,an ahp evaluation model is established for the optimal scheme of urban underground comprehensive pipe corridor.The calculation methods,evaluation standards and evaluation levels of each evaluation index were summarized,and finally a risk evaluation index system for the construction of urban underground comprehensive pipe corridor was formed.The overall ranking of the scheme layer was conducted,and the best scheme was selected reasonably among the three pre-selected schemes:overburden thickness 2.2m,horizontal distance 3m.Through the analytic hierarchy process and expert decision method,the objectivity and reliability of the evaluation results are improved,and the optimization scheme of underground comprehensive pipe corridor construction is scientifically selected to provide references for the subsequent construction and maintenance of comprehensive pipe corridor. |
