Milling and blasting combined construction method for water-rich sandy dolomite stratum tunnel

Abstract

The invention discloses a milling and blasting combined construction method for a water-rich sandy dolomite stratum tunnel. The milling and blasting combined construction method aims to effectively reduce the risks of collapse, water inrush and mud gushing of an arch part under the condition of broken surrounding rock, control tunnel over-excavation and under-excavation, accelerate the construction progress, shorten the unit cycle construction time and effectively reduce the tunnel construction cost. The milling and blasting combined construction method comprises the following steps that (1) preparation work is performed before construction; (2) core soil of an upper step is excavated through weak blasting, an excavator of the upper step digs slag to a middle step and a lower step, reserved rock mass of the upper step is milled and excavated by adopting a cantilever excavator, and an upper step surrounding primary support is constructed in time after finishing to a designed outline; (3) core soil of the middle step is excavated through weak blasting, an excavator of the middle step digs slag to the lower step, a middle step left side reserved rock body and a middle step right sidereserved rock body are milled and excavated by adopting the cantilever excavator, and a middle step left side primary support and a middle step right side primary support are constructed in time afterfinishing to a design outline; (4) a rock body of the lower step is excavated through weak blasting, and a lower step left side primary support and a lower step right side primary support are constructed; and (5), a rock body of an inverted arch is excavated through weak blasting, and an inverted arch primary support is constructed.

Description

technical field [0001] The invention relates to the field of tunnel construction methods, in particular to a milling and blasting combined construction method for tunnels in water-rich sandy dolomite formations. Background technique [0002] With the continuous improvement of my country's national railway network, it is inevitable to build railway tunnels under complex geological conditions in mountainous areas. In particular, when tunnels pass through water-rich dolomite sandy strata, the Frequent changes, dense rock mass before disturbance, and extremely poor self-stability under the erosion of water” and other characteristics, landslides, water inrush and mud gushing often occur during construction, which seriously endanger the safety of tunnel construction. [0003] At present, the drilling and blasting method is still the main method in tunnel construction. The impact of blasting on the surrounding rock and supporting structures is reduced by smooth surface or pre-splitt...

AI Technical Summary

Problems solved by technology

[0007] 1. The space of the pre-cut grooves is narrow, and it is difficult to construct the steel frame, and it is impossible to construct the radial system anchors in time, which affects the bearing capacity of the supporting structure;

[0008] 2. The core soil is constructed by milling and excavation, and the work efficiency is low. However, when blasting is used for excavation, it is easy to cause greater damage to the initial support due to blasting disturbance or mechanical slag discharge;

[0009] 3. If the surrounding rock in front of the face of the tunnel is broken and the groundwater is abundant, construction in the pre-cut groove space will easily cause the surrounding rock of the arch to collapse, and the construction safety risk is high

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