Study On The Safety Factor Of Tunnel Proximity Pile

Slop foundation and tunnel are the three main research objects of the Geotechnical Engineering. The stability analysis of soil can be carried out in the former two, and only the stability of tunnel rock mass can not be analyzed precisely until now. It is still based on some experiences, which restrictes the design of tunnel.There is no better method of analysis about the stability of tunnel under pile loads and the judge is not offered current.During the design process ,people mainly base on existing experience of distance between pile and tunnel and propose some control principles.The application of strength reduction FEM in the stability analysis of tunnel under pile loads and design and displacement release factor of tunnel were studied in detail in this thesis.Main tasks and key innovations are follows:â‘ The influence factors of stability of tunnel by pile loading such as strength of rock mass, pile load, distance between pile and tunnels, depth of pile were studied. Through analyzing the calculation result of safety factors,we found critical distance is one times the diameter of the tunnel from the side wall.When the distance of pile and tunnel Within the critical distance,load of pile has greatly influence on safety factor of tunnel.when the load increases twice, safety factor will reduce about 1/4. Rock mass strength of surrounding rock has greatly influence on safety factor of surrounding rock.Roce mass was reduced from sandstone to shale, safety factor of surrounding rock will reduce 1/4.â‘¡With the heading propeling,rock mass strength parameters(cohesion,internal friction angle) and the initial stress state(poisson's ratio) has greatly influence on the release factor of surrounding rock displacement. Deformation modulus has little effect to the release factor of surrounding rock displacement,affect the volume of about 1%.The greatest impact volume is Poisson's ratio effects on the side walls, reaching more than 20%, but its impact on the vault and the bottom will become relatively small.In the strength parameters of the single-factor analysis, when it reaches a certain value and continues to increase again , the surrounding rock deformation and displacement will tend to release more than a fixed value. the release factor of surrounding rock displacement focused o n monitoring section 0.5D, the accounting for the total displacement of 70% to 80%. Especially when the working face by the monitoring section 0.5D, displacement release for the total displacement of 50% to 60%.â‘¢When the rock releasing factor of more than 60%,under the same releasing factor, with the reduction of rock strength, safety factor of tunnel will reduce rapidly.As for the V grade rock, the tunnel's safety factor is less than 1.So when the strength of surrounding rock is lower,the construction of pile foundation should not be built.Intensity of a high rock safety factor high, greater security reserve.