Anti-seepage method for deepwater hard rock steel sheet pile cofferdam

Abstract

The invention discloses an anti-seepage method for a deepwater hard rock steel sheet pile cofferdam, which comprises the following steps of: drilling a hole guide groove in a field rock-soil layer by using a hole guide machine so as to insert and fix the lower end of a steel sheet pile; after the hole guide groove is formed, throwing coarse sand for filling the groove hole firstly, and then throwing clay for filling the hole guide groove till a groove opening is filled; driving a steel sheet pile which is manufactured in advance and provided with a grouting pipe into the throwing and filling soil of the hole guide groove till the built-in depth which is designed in advance is reached, and after the steel sheet pile enters the position, injecting cement mortar into the hole guide groove through a grouting pipe with a hole; before the cement mortar is solidified, arranging an ultrasonic density sensor in the groove to monitor the density change of the soil body in the groove in real time, continuing grouting when the density of the soil body does not reach a design value, and stopping grouting once the density of the soil body reaches the requirement; and pumping water from the inner side of the steel plate cofferdam after the cement mortar is solidified. Most double-wall steel cofferdam construction schemes can be replaced, the number of temporary cofferdam projects is greatly reduced, and the application range of the steel sheet pile cofferdam technology is greatly expanded.

Description

technical field [0001] The invention relates to a cofferdam anti-seepage method, in particular to a deep-water hard rock steel sheet pile cofferdam anti-seepage method. Background technique [0002] The construction of bridge caps requires the use of cofferdams to provide a dry environment for operations. In domestic deep water (above 15m above water) and similar hard rock geological conditions, the bedrock is generally blasted underwater, and then the double-walled casing is used to float and lower it into place for construction. It mainly has the following problems: [0003] The lowering of the double-walled cofferdam requires underwater blasting of the bedrock. The processing of the cofferdam is difficult, and the construction requires a large amount of marine machinery and equipment, and it is difficult to recycle. The cost is high and the construction period is long; the construction of the double-walled steel cofferdam requires a large thickness The bottom cover concr...

AI Technical Summary

Problems solved by technology

[0003]Double-walled cofferdam requires underwater blasting of the bedrock. The cofferdam is difficult to process, requires a large amount of marine machinery and equipment, and is difficult to recycle and expensive. The construction period is long; the double-wall steel cofferdam is used for construction, and a large thickness of bottom-sealing concrete is required to meet the stability requirements of the base after pumping (generally, the water depth increases by 2-3m, and the bottom-sealing concrete needs to be increased by 1m), which greatly increases the excavation of the foundation pit. The depth of the cofferdam requires deeper soil anchoring, and at the same time, the safety risk during the excavation of the foundation pit is doubled; if the steel sheet pile cofferdam is used for construction, the hard rock cannot be driven in, and the depth of the steel sheet pile is not deep enough for construction; Conventional steel sheet pile cofferdams are generally constructed by pumping water first and then installing internal supports, but for cofferdams in deep water areas, this method cannot meet the stress requirements under high water heads;

[0004] For the internal support construction first, the traditional method is to use large floating cranes or distributed jacks for integral lowering. High-altitude operations and other issues, and the decentralization method is complicated, the safety risk is high, and the economy is poor

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