1. Guide wall
The guide wall is usually a reinforced concrete structure poured on-site. The main functions are: to ensure the geometric size and shape of the underground diaphragm wall; to store part of the mud to ensure the stability of the liquid level during the construction of the trench; to bear the load of the trenching machinery, to protect the soil wall of the notch from damage, and to be used as the installation of the steel frame Benchmark. The depth of the guide wall is generally 1.2 to 1.5 meters. The top of the wall is 10-15 cm above the ground to prevent the inflow of surface water from affecting the mud quality. The bottom of the guide wall should not be located in loose soil layers or locations where the groundwater level fluctuates.
2. Mud protection
The mud is applied to the wall of the groove to protect the shape of the deep groove, and the mud is replaced by pouring concrete. The mud material is usually composed of bentonite, water, chemical treatment agents and some inert substances.
The role of the mud is to form an impermeable mud skin on the tank wall, so that the hydrostatic pressure of the mud can effectively act on the tank wall to prevent groundwater seepage and peeling of the tank wall, maintain the stability of the wall, and the mud and suspended soil The slag and the function of carrying the slag out of the ground.
3. Grooving construction
The special machines used in China to form grooves include: rotary cutting multi-head drills, guide grabs, impact drills, etc. The construction should be selected according to the geological conditions and the depth of the wall. Generally speaking, the soil is soft, and when the depth is about 15 meters, you can choose the ordinary guide plate grab; for the dense sand or gravel-bearing soil layer, you can choose a multi-head drill or a heavy hydraulic guide plate grab; when there are large particles of gravel or rock foundation It is advisable to use percussion drills for medium-sized grooves. The unit length of the trough section is generally 6 to 8 meters, which is usually determined based on the soil condition, the weight of the steel frame, the structural size, and the division of sections. After forming the tank, let it stand for 4 hours, and make the specific gravity of the mud in the tank less than 1.3.
4. Underwater pouring concrete
The pipe method is carried out according to the underwater concrete pouring method, but in order to prevent the mud from mixing into the concrete before the pipe is used to pour the concrete, a pipe plug can be hung in the pipe and the mud in the pipe can be squeezed out by the pressure of the poured concrete. Concrete should be poured continuously and the amount of concrete poured and the rising height measured. The overflowed mud is returned to the mud sedimentation tank.
5. Wall joint treatment
The underground continuous wall is composed of many wall sections. In order to maintain continuous construction between the wall sections, the joint adopts the lock pipe technology, that is, before pouring the concrete of the groove section, a diameter and groove are pre-inserted at the end of the groove section. Steel pipes of equal width, namely lock pipes, are slowly pulled out after the concrete has initially set, so that the ends form a semi-concave joint shape. There are also rigid joints according to the force requirements of the wall structure, so that two successive wall sections can be connected as a whole.
1. Guide wall