Large filling type karst cave geological tunnel foundation reinforcing structure and construction method thereof

Abstract

The invention discloses a large filling type karst cave geological tunnel foundation reinforcing structure. A plurality of rows of grouting steel pipe piles are arranged at the bottom of a tunnel inverted arch in the length direction of a tunnel and go deep into underground bedrock or a soil body with a certain depth, a graded broken stone hardcore is laid above the steel pipe piles at the bottomof the tunnel, and a concrete bearing platform is poured above the graded broken stone hardcore. The construction method comprises the following steps of on-site surveying and setting out, drilling, hole cleaning and hole inspection, steel floral tube installation, primary grouting, secondary grouting and tunnel inverted arch bottom concrete bearing platform construction. The requirements for theconstruction quality and the service life of a karst cave geological tunnel foundation can be met, the bearing capacity is high, subsidence of the karst cave geological tunnel foundation is effectively controlled, the mechanical property of the cast-in-place pile is good, the piles are not prone to breakage, and hole collapse and blockage are effectively controlled in the hole forming process of the cast-in-place pile; and the whole foundation reinforcing structure is beneficial to maintaining water and soil stability in a tunnel mountain, and the natural water system environment is not affected.

Description

technical field [0001] The invention relates to the technical field of tunnel foundation construction, in particular to a foundation reinforcement structure of a large-scale filled karst cave geological tunnel and a construction method thereof. Background technique [0002] To build expressways in karst mountainous areas, it is necessary to build bridges when encountering water and open holes when encountering mountains. The ratio of bridges and tunnels is even as high as 80%. Affected by the development of large karst caves, a large amount of soft soil such as sand, clay, black soil, and clay with breccia and gravel is filled inside. Due to the insufficient bearing capacity of the soft soil layer and the weak foundation, it cannot meet the bearing requirements of the road surface, so it is necessary to strengthen and reinforce the geology of the karst cave. In areas with strong karst development, the tunnel crossing the mountain belongs to the karst peak-cluster landform, ...

AI Technical Summary

Problems solved by technology

[0004] When using the tree root pile reinforcement method to reinforce the tunnel foundation of the karst filled karst cave landform, there are still some difficulties: 1. The internal space of the large filled karst cave is huge, filled with a large amount of soft soil, when the cast-in-situ pile passes through the karst cave When the inner cavity is soft, the soft soil cannot give good support to the side wall of the cast-in-place pile, which is equivalent to a long section of the cast-in-place pile in a suspended state, and the cast-in-situ pile without reinforcement is easy to break without sufficient side wall support The strength of the cast-in-place pile can be greatly improved by setting the steel cage in the cast-in-place pile compared with the cast-in-place pile without the steel cage, and it can prevent the pile from breaking, especially on the road surface of the expressway tunnel, which carries large trucks. The strength of the cast-in-place pile determines the The load-carrying capacity of the road surface; while placing the reinforcement cage in the pouring hole less than φ300mm, it is difficult to lower the reinforcement cage due to the large depth, the reinforcement cage is small in size, the length to diameter ratio is too large, and the manufacturing process is time-consuming and labor-intensive; 2. In areas where underground water veins and karst caves frequently occur in karst landforms, during the drilling process, when dense karst caves are encountered, the holes are prone to collapse, and then the cast-in-situ piles are blocked repeatedly, making it very difficult to clean the holes, which greatly delays the construction period

Therefore, the reinforcement construction of the tunnel foundation in the karst cave landform has always been a thorny problem in front of the construction personnel.

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