Grading loading method for variable-stress path well point plastic drainage vacuum preloading seepage consolidation

Abstract

The invention relates to a grading loading method for variable-stress path well point plastic drainage vacuum preloading seepage consolidation. The method is characterized in that in a vacuum preloading stage, vacuum pumps perform vacuumization in a grading loading manner, and the operation that vacuum pumps perform vacuumization in the grading loading manner includes the following steps that the vacuum pumps perform grading loading on the first stage, the treatment area of each vacuum pump ranges from 1800 square meters to 2000 square meters, the negative pressure of the first segment of a header pipe is full-meter 100 kPa, and the pressure of the tail end of the header pipe is not lower than 90 kPa; when sedimentation meets the requirement that sedimentation in continuous three days is not larger than 3 mm, the vacuum pumps perform grading loading on the second stage, and the treatment area of each vacuum pump ranges from 1300 square meters to 1500 square meters; when sedimentation meets the requirement that sedimentation in continuous three days is not larger than 3 mm, the vacuum pumps perform grading loading on the third stage, the treatment area of each vacuum pump ranges from 800 square meters to 1000 square meters or below; and in the same way, when sedimentation meets the requirement that sedimentation in continuous five days is not larger than 2 mm, the vacuum preloading treatment requirement is met. The grading loading method has the beneficial effects of being easy to operate, low in cost and good in construction effect.

Description

technical field [0001] The invention relates to a treatment method for weak ground, in particular to a stepwise loading method for plastic drainage, vacuum preloading, seepage consolidation and staged loading at variable stress path well points. Background technique [0002] According to 7.1.1 of the "Code for Design of Building Foundations" (GB5007-2011), weak foundations refer to foundations mainly composed of silt, muddy soil, flushing soil, miscellaneous filling soil or other highly compressive soil layers. Before building construction on the weak foundation, it is necessary to consolidate the weak foundation first. The conventional consolidation treatment methods are as follows: [0003] 1. Conventional vacuum preloading reinforcement. Conventional vacuum preloading reinforcement "on land and under water in rivers, seas, lakes and swamps" soft soil foundations all need to be laid with sealing film and sand cushion, but there are the following disadvantages: [0004] 1....

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Problems solved by technology

[0004] 1. The construction of large-area sealing membranes is difficult, and vacuum preloading on land requires a lot of manual laying of membranes with a low degree of mechanization, especially the construction of underwater vacuum preloading sealing membranes is more difficult;

[0005] 2. The PVC sealing film has low strength and is easy to be damaged and leak air. The cost of the second layer of sealing film and the first layer of geotextile is high, and it is difficult to find the air leakage point;

[0006] 3. A large number of PVC sealing films are not environmentally friendly;

[0007] 4. The surface under the film can reach a maximum negative pressure of 80kPa, and the negative pressure transmission loss to the deep part of the soil layer is fast. Generally, the loss of negative pressure per meter to the deep part is about 10kPa. The effective reinforcement depth is shallow;

[0008] 5. The loading surface is on the original ground surface or the backfilled land surface. Even if the surface sealing film does not leak, the slow air leakage of the shallow soil around the reinforcement area cannot be ignored, especially in the case of long-term loading for about 90 days, when the groundwater level drops to The degree of air leakage in shallow soil around a certain degree of reinforcement area is even more worrying

[0009] 2. The improved vacuum preloading reinforcement has the following disadvantages:

[0010] 1. The sand-removing cushion layer is changed to the mode of direct connection of plastic slabs with hand-shaped joints, and the mode of indirect negative pressure transmission is changed to direct negative pressure transmission mode, but it still needs a sealing film, and the maximum negative pressure loading surface is still on the surface;

[0011] 2. The sealing layer is formed by blowing and filling mud, or the vacuum branch pipe is directly connected to the plastic discharge into the soil for about 1.5 meters, or the vacuum filter tube is about 3 meters underground, and the side blister row replaces the sealing film. The dredging fill mud loses water, consolidates and cracks, the groundwater level drops rapidly, and the sealing effect is greatly reduced;

[0012] 3. The ultra-soft soil for land reclamation cannot be mechanically constructed. First, artificially insert the shallow layer of plastic drainage vacuum preloading, and then do deep vacuum preloading after the foundation strength is suitable for mechanical construction. The principle and process of conventional vacuum preloading are almost the same, only the simple difference between manual and mechanical, the process is more complicated, the cost is high, and the efficiency is low;

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