The construction method of sprayed concrete for the mobile formwork of the inner mold of the airbag and the initial support of the tunnel

Abstract

The invention discloses a mobile formwork for an airbag inner mold and a construction method for sprayed concrete for initial support of a tunnel. Telescopic support device, the telescopic support device is installed on the mobile support bent frame and it is located inside the inflatable formwork; the construction method includes steps: 1. The mobile formwork of the inner mold of the airbag is moved forward to the position; 2. The initial support of the tunnel is shotcrete Construction; 3. Sprayed concrete construction for the initial support of the next tunnel segment; 4. Repeat step 3 several times until the construction process of the sprayed concrete for the initial support of all tunnel segments is completed. The invention is reasonable in design, simple in construction and good in use effect. The rebound rate of shotcrete for initial support of tunnels is effectively controlled through the inner mold of the airbag, and the construction efficiency is high, the construction period is short and the construction quality is high, and the spraying of initial support of tunnels can be realized. Concrete has zero rebound.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a mobile mold base for an airbag inner mold and a construction method for sprayed concrete for primary support of a tunnel. Background technique [0002] The shotcrete construction technology has been widely used in the initial support of tunnel construction, and is an important part of the anchor shotcrete support in the new Austrian method construction. In terms of technology, shotcrete is divided into four types: dry spraying, tidal spraying, wet spraying and mixed spraying. Because the strength of dry spraying can only reach about 15MPa, and the working environment at the construction site is poor, labor intensity is high, and material waste is large. The production efficiency is low, and it can no longer adapt to the current production technology requirements, so the dry spraying process has faded out of the construction site. The wet spraying proces...

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Problems solved by technology

The above-mentioned traditional construction methods mainly have the following defects: First, the waste is large: during construction, due to the collision of the sprayed grout on the surrounding rock and the steel reinforcement of the supporting steel frame, a large amount of springback material is generated, and the springback material must not be reused according to the specification. The commonly used springback material reaches 10% to 20%, and even reaches more than 30% for cold weather areas; taking the Queershan Tunnel as an example, the unit price of the spraying material cost per cubic meter is 1135.62 yuan, and the spraying material for the whole tunnel The waste is as high as 5.8 million yuan; therefore, reducing the rebound rate of shotcrete for the initial support of the tunnel is an important cost control point in tunnel construction, but the best controlled rebound rate is 10% to 15% at present, and the rebound rate is relatively large. Big; Second, heavy pollution: Shotcrete operation is the most polluting process in tunnel construction. During construction, the sprayed grout collides with the surrounding rock and the steel reinforcement of the supporting steel frame, generating a large amount of dust particles. Even if the construction personnel wear protective equipment, It still has a huge impact on the health of construction workers; third, long working hours: during tunnel construction, it generally takes about 4 hours for a cycle of sprayed concrete construction, and construction in this heavily polluted environment for a long time will seriously damage the health of construction workers , takes a long time in the entire tunnel construction cycle, and costs a lot; Fourth, low quality: shotcrete construction has high technical requirements for operators, and it is extremely difficult for general workers to meet the quality requirements, and there are generally uncompacted, uneven, thick not enough happens

However, after various improvements and improvements, even if all the factors that affect the rebound rate too much have reached the optimal control parameters, the tunnel construction in plain areas generally can only control the shotcrete rebound rate as follows: vault shotcrete rebound rate The rebound rate of sprayed concrete on the side wall is about 20% and the rebound rate of shotcrete on the side wall is about 15%. Due to the influence of low pressure and low temperature in high altitude areas, the rebound rate of shotcrete can only be controlled as follows: the rebound rate of sprayed concrete on the vault is about 30%. , the rebound rate of shotcrete on the side wall is about 25%, which cannot eradicate the cost waste and construction environmental pollution caused by the rebound rate

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