This support effect disappears when the pipe jacking machine is pushed out, because the pressure of bentonite is also stopped, so when the pipe jacking machine is jacked up again, as a first measure, it must be restored. This support role. Before starting the main and intermediate pressure stations of the pipe jacking machine, it is necessary to first inject the bentonite suspension into the entire pipeline for a sufficient time. The time needs to be long enough because the suspension can only flow slowly between the surface of the pipe and the surrounding soil layer under normal flow limits.
After a long pause, it is better to use a suspension with a lower flow limit when restarting the top pipe of the pipe, that is, the content of bentonite is lower than the content corresponding to the standard particle size . In order to enable the suspension to reach the injection nozzle quickly without first squeezing the hardened substance in the bentonite pipe with a high pressure, it is better to empty the bentonite pipe before long-term pause.
After evacuating, it is inevitable that pengrun mud will be everywhere. In order to play the same role as emptying the pipeline without causing the trouble of soiling the pipeline, you can pump fresh water into the pipeline before shutting down the bentonite pressure delivery system. The amount of water should be exactly as accurate as the pipeline Volume. When the pipe jacking machine is lifted, the water stored in the pipe must be discharged with a small pressure until the suspension flows out.
An important factor in the construction of the rectangular pipe jacking machine is the pipe joint, which has the following functions:
1. The pipe jacking machine transmits longitudinal force between the pipe when jacking up;
2. Transverse force when the direction of the pipeline changes;
3. Seal between tubes.
To reliably transfer longitudinal forces, elastic cushions need to be sandwiched in the seams of the pipes. The gasket must be able to transfer the ejection force from one tube to the next tube. This high unscrewing force can generate a pressure of 300 kg per square centimeter. In this case, the gasket must be quite flexible so as to be able to compensate for unevenness in the end face of the pipe. In the process of transferring loads, the cushion can and must be deformed without being hardened. The elasticity of the gasket should be as small as possible, because when the jacks of the main and intermediate pressure stations are unloaded, the elasticity of the gasket will cause the rebound of the tube from one section to the next, resulting in the ejection effect in each case. Part of it was lost after uninstalling.
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