Method for constructing tunnel with low-half cross section being dry powder and fine sand layers

Abstract

The invention particularly relates to a method for constructing a tunnel with a low-half cross section being dry powder and fine sand layers, which solves the problems of slow construction progress and large safety risk which exist in the existing tunnel construction, and comprises the steps of: a, performing forepoling after survey lofting; b, digging out an arc pilot tunnel, immediately and firstly spraying concrete, and constructing primary anchor-plaster retaining; c, constructing an advanced horizontal jet grouting pile as well as a slant jet grouting pile; d, separately excavating a middle step according to an upper part and a lower part; e, constructing the slant jet grouting pile on a lower step; f, separately excavating the lower step according to the upper part and the lower part; g, excavating a tunnel bottom from the left side and the right side of the tunnel in a subsection way for anchor-plaster retaining; and h, constructing an inverted arch after excavating the reserved core soil, wherein the construction of the inverted arch closely follows the lower step all the time, and then, constructing secondary lining. The method plays the role of controlling the convergence and subsidence of the primary anchor-plaster retaining; and moreover, the disturbance to the fine sand layers is reduced, the subsidence of the tunnel is effectively controlled, the extruded placement of a tunnel face is strictly regulated, and the deformation of the tunnel face is controlled.

Description

technical field [0001] The invention relates to a construction method of a tunnel, in particular to a construction method of a tunnel with a dry fine sand layer in the lower half section. Background technique [0002] With the rapid development of my country's high-speed railways, highways, and underground projects, various unfavorable strata will be encountered during tunnel construction. The dry silty sand stratum has the following characteristics: (1) It is mainly light yellow-brown silty fine sand and fine sand, with particles The particle size is mainly concentrated in the range of 0.075-0.25mm, accounting for about 80%-93% of the total weight. The particles are relatively uniform and the particle gradation is poor; (2) dry, with a natural moisture content of only 2%-4%; (3) Dense state; (4) low cohesion, cohesion 0-2kPa, internal friction angle 30°-32°. The dry silty sand layer has high sensitivity and strong thixotropy. During the construction process, it will cause di...

AI Technical Summary

Problems solved by technology

[0003] The present invention aims to solve the problem that the grouting or freezing method is not suitable for the grout to spread in the tunnel with the dry powder and fine sand layer in the lower half section, the phenomenon of sand sliding and sand gushing is easy to occur after excavation, the tunnel cannot be closed quickly, the construction progress is slow, and there are safety risks. To deal with big problems, a construction method for tunnels with dry silt and fine sand layer is provided in the lower half section