Quality control and guarantee measures of pipe jacking construction
Because this project is a pipe jacking construction, the pipe jacking depth is relatively deep, and the section where the pipe jacking passes is close to buildings and structures, which requires high quality and safety control of pipe jacking. In the process of construction, all aspects of quality and safety control should be done well to ensure the smooth progress of the project construction.
The key to the quality control of pipe jacking construction is the control technology of pipe jacking axis orientation, including the positioning of pipe jacking axis (midline) and the control technology of pipe jacking elevation. In the process of construction, the positioning, production, settlement and pipe jacking control of the working well need to be closely organized and carefully constructed around the core to achieve the design function goal of the project.
1, measuring system:
Whether the pipe jacking can be constructed according to the design drawings, the positioning and elevation control of the working well is an extremely important link. In the process of construction, our company will use precision total station and compact level to measure. Carefully measure the jacking direction of the axis, the direction of the working well and the receiving well, and the jacking construction of the construction unit of the adjacent bid section, and also strictly check the axis direction of the pipe jacking. Elevation control is related to the flow and flow direction of the pipeline. During construction, it must be strictly controlled, with one footage per jacking, that is, check the water level elevation once, and control the construction water level elevation within the acceptance standard.
2, pipe jacking process quality control:
(1) staffing:
Pipe jacking construction equipment includes tool head, jack button, high-pressure oil pump system, relay room, laser positioning device, drag reduction mud mixing and grouting system, etc. , high requirements for the use of equipment. Our company will be equipped with enough engineering and technical personnel to carry out the construction of this project, and equipped with enough professional and technical personnel to carry out the construction of key processes such as pipe jacking and measurement to ensure the quality of pipe jacking.
(2) Preparation of machine materials:
In the process of pipe jacking construction, firstly, the pipes needed for pipe jacking, bentonite needed for drag reduction mud and ingredients used to replace cement slurry should be prepared to ensure the smooth progress of pipe jacking construction. In addition, the sealing flange ring must be made according to the pipe jacking diameter of the working well. The flange ring is made of steel plate with two foam rubber water-stop rings and spare parts. The jacking iron connected with jack and pipe jacking should also be equipped at the same time.
(3) pipe jacking:
Calculate the jacking force according to the pipe jacking length and pipe diameter, and equip with enough jacks and relay rooms to ensure smooth jacking.
The geological structures of this project are mostly medium sand and fine silt with high friction. Thixotropic mud should be added during construction to reduce resistance, and the jacking length should be controlled within 50m. A relay room should be set every 50m to ensure the jacking force.
In the process of pipe jacking, continuous operation is needed to prevent shutdown, pipe grabbing and stuffy roof. During pipe jacking, the jacking direction and elevation should be strictly controlled, and measurement and rectification should be carried out at any time.
After the stage pipe jacking is completed, the cement slurry grouting replacement process will be carried out immediately, and the drag reduction slurry will be replaced with cement slurry to ensure the stability of the pipeline. The grouting hole of displacement cement slurry can be filled with drag-reducing cement slurry grouting hole and high-pressure mud pump.
(4) Control measures:
During the construction period, 1 professional manipulator will be arranged to realize the rotation, rectification control, pressure display and real-time monitoring of the tool head (the tool head is equipped with a camera and the console is equipped with a TV). Jacking, observing the pressure gauge of the working warehouse, and adjusting the mud-water balance to keep a certain pressure in the designated warehouse, so that the earth pressure in the warehouse is in coherent balance with the active earth pressure of the working face, and the passive earth pressure is too large, resulting in ground uplift; The active earth pressure is too high and the ground sinks, so it is very important to control the jacking and mud discharge speed.
3. Mud system:
In the process of jacking, thixotropic mud is often needed to reduce the jacking resistance. Thixotropic mud system consists of three parts: mud mixing, grouting and pipeline. Slurry mixing is to mix the grouting material with water to form the required slurry (it should be left standing for 24 hours before use). Grouting is carried out through grouting pump. According to the pressure gauge and flowmeter, control the grouting pressure (the pressure is controlled at 1. 1 ~ 1.2 times the water depth) and the grouting quantity (controlled by the metering bucket). Pipes are divided into main pipes and branch pipes. The main pipe is installed inside the pipeline, and the branch pipes transport the slurry from the main pipe to each grouting hole. Grouting holes are arranged as follows: one for tool head, one for 1 concrete pipe, and one grouting hole (the interval between two concrete pipes is 7.5m).
After jacking a section of pipeline, dismantle all pipelines (power cables, signal wires, oil pipes and thixotropic mud pipes), lift concrete pipes, install all pipelines (power cables, signal wires, oil pipes, mud pipes in and out, thixotropic mud pipes) and continue jacking.
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