Construction method of underwater large-depth open caisson penetrating through hard and difficult-to-break soil layer

Abstract

The invention relates to a construction method of an underwater large-depth open caisson penetrating through a hard and difficult-to-break soil layer. The construction method comprises the steps thatthe open caisson adopts non-drainage sinking, an overwater working platform is placed on the water surface in the open caisson, high-pressure crushing equipment and underwater mud taking equipment areinput on the platform; the high-pressure crushing equipment is adopted to break layer by layer, a drill rod of the high-pressure crushing equipment drills into the hard soil layer by the specific depth, ultra-high-pressure water flows are sprayed through spraying nozzles of the high-pressure crushing equipment to cut soil, and the soil is crushed into mud; and after the high-pressure crushing equipment fully and effectively crushes the hard soil, the underwater mud taking equipment is adopted, and through the air mud suction principle, the mud formed after the soil is crushed is taken out ofthe open caisson through a mud discharging pipeline in the mud taking equipment. The method that the working platform is placed on the water surface in the open caisson, the downhole soil is crushed at the high pressure firstly, then the mud is taken, and layer-by-layer sinking is achieved is adopted, the crushing mud taking effect is good, thus the open caisson safely and smoothly penetrates through the hard and difficult-to-break soil layer, and the quality and safety of sinking of the open caisson are guaranteed.

Description

technical field [0001] The invention relates to a municipal caisson construction technology, in particular to a construction method for an underwater large-depth caisson to pass through a hard soil layer that is difficult to break. Background technique [0002] A caisson is a type of underground structure and deep foundation. Generally, the ground surface is made into a shaft-like structure, and then the caisson is gradually sunk under the action of its own weight by continuously digging soil from the well under the protection of the well wall. After reaching the predetermined design elevation, the bottom is sealed to build the interior. structure. Caissons are widely used in the construction foundations of bridges, chimneys, and water towers. They can also be used as deep well structures such as water pump houses, underground oil depots, and pool shafts, as well as working wells for shield tunneling or pipe jacking. , the impact on adjacent buildings is relatively small. ...

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Problems solved by technology

[0021] ① With the increase of subsidence depth, the speed of borrowing soil decreases rapidly, and the influence of "time and space effect" of water and soil flow will greatly reduce the efficiency of effective soil subsidence;

[0023] ③Because the whole process of caisson is submerged under water, the water depth in the well is close to 40m when passing through the hard soil layer in the final sinking stage. The lower grab and line of sight are obstructed by the water surface, making it impossible to observe the bottom of the well, and the grab is difficult to operate

At the bottom of the caisson, there are cross bottom beams and high blade treads. Affected by the vertical projection relationship, facing the hard and self-supporting soil layer, the grab bucket cannot effectively grasp the soil below the bottom beams and blade treads. The bottom of the well is covered by high-hardness clay, which hinders the sinking of the caisson, and it is difficult to carry out the sinking construction of the caisson with grab buckets

[0024] ④ If the commonly used air dredging equipment is used, it is composed of high-pressure water inlet pipe, air inlet pipe and mud discharge pipe. The crushing injection pressure of the water inlet pipe is usually about 3MPa. Under the condition of 40m water depth, the jet pressure of the nozzle is greatly affected, and The soil layer is extremely hard, the jet pressure crushing effect is extremely weak, the soil is difficult to be crushed and sucked out of the well, and the commonly used air suction mud equipment is not suitable for the construction of underwater large-depth caissons passing through hard soil layers that are difficult to break

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