[0032] The specific process steps of this method are as follows (dynamic consolidation takes dynamic consolidation as an example):
[0033] Step 1: Excavate the drainage ditch
[0034] For large-area weak foundations, adopt light well plastic drainage point dewatering reinforcement technology, and then several communities can be set up in the area to be reinforced. Generally, a community is 5000~10000m 2. Open trenches are excavated between the communities, and the open trenches between the communities are connected to each other to form a drainage network. A certain number of water collection wells are set at the junction of the open trenches, and the open ditch water is discharged into adjacent rivers by gravity or forced drainage.
[0035] Step 2: Arrange composite well points formed by light-weight well point pipes combined with plastic drainage plates (referred to as light well plastic drainage well points) and vacuum composite well points for dewatering
[0036] a. Shidaqingjing plastic drainage point and peripheral pipe sealing
[0037] For the soft foundation to be treated, arrange light well plastic drainage points according to the design requirements and geological conditions, and the spacing between the well points is 4.0×4.0m, such as figure 1. The length of the plastic drainage board is determined according to the depth to be treated. There are two ways to insert the plastic drainage board:
[0038] One is the mechanical insertion method (reinforcement depth below 6.0m):
[0039] That is, the commonly used board inserting machine is inserted into the plastic drainage board of the required depth. After the inserting tube of the board inserting machine is pulled out, immediately insert the light well point pipe into the socket with the plastic drainage board. To ensure the precipitation effect, insert the light well While tapping the pipe, put sand filter material between the light well point pipe in the jack, the plastic drainage plate and the hole wall of the jack, and press the end of the plastic drainage plate into 0.5m below the ground surface. Fill the material to about 0.5m away from the hole of the jack, and then seal the hole of the jack with clay tightly to prevent air leakage due to the end of the plastic drainage plate exposed on the ground when the light well is dewatering, such as image 3.
[0040] The other is the water-punched hole insertion method (reinforcement depth above 6.0m):
[0041] Because of the need for shallow reinforcement, it is completely possible to directly insert the plastic drainage board with a light well point pipe. The method is: first cut the plastic drainage board to a certain length, and turn the plastic drainage board back with a rope at one end of the plastic drainage board. Insert the light well point pipe and the plastic drainage plate into the hole at the same time (attached figure 2 ), after the water is flushed into the hole, insert the light well point pipe and the plastic drainage plate into the hole to form a light well plastic drainage point. The other end of the plastic drainage plate is pressed into the surface 0.5m below the surface and in the hole Put sand filter material between the light-weight well point pipe, plastic drainage plate and the hole wall of the socket to fill and fill, and press the end of the plastic drainage plate into 0.5m below the surface, and fill the sand filter to 0.5m from the hole of the socket Right and left, then seal the hole of the jack tightly with clay.
[0042] b. Installation of precipitation equipment
[0043] According to the layout of the plastic wells of light wells, the location of the water collecting main shall be arranged. When laying, the water collecting main shall be discharged first, and then the light well point pipe and the plastic drainage board shall be buried by mechanical insertion method or water flushing method, and then the light pipe shall be used to make the light The well point pipe is connected with the water collecting main pipe, and finally the pumping equipment such as vacuum pump and balancer is installed. The light well point pipe should be buried in the center of the water punching hole to avoid plugging the filter pipe into the mud. There should be a slope of 3% to 5% from the header to the pumping device, such as Figure 4.
[0044] c. Vacuum precipitation, the vacuum degree should be controlled between -0.06~-0.08MPa, and should not be lower than -0.04MPa. The first vacuum drainage time is 7-10 days, and the second vacuum drainage time is 7-10 days. The interval between the second vacuum drainage is determined according to the dissipation time of the extra-static pore water pressure of the soil after ramming, generally between 7-15 days , In actual construction, it can be determined according to soil conditions. In actual construction, appropriate adjustments can be made according to specific conditions (soil moisture content, total on-site drainage, precipitation curve, etc.).
[0045] d. The end of precipitation
[0046] The control index of the light well plastic drainage point after precipitation is: the allowable error of the optimal water content after precipitation is 3% to 5%, and the groundwater level is controlled to be stable below 3m from the surface. When the observation result meets the control index requirements, the next process can be constructed.
[0047] Step 3: Dynamic consolidation (take dynamic compaction as an example)
[0048] When the soil moisture content meets the requirements for design and dynamic consolidation construction, remove the light well point pipe from the light well plastic drainage point, and lay a dynamic compaction point in the soft soil foundation area that needs to be reinforced for the first round of compaction , The first round of point ramming is arranged according to a 4.5m square (or the points can be arranged according to the geological conditions or design requirements), after ramming, flatten, and the second round of light well plastic drainage points are arranged, the method is the same as the first place, and the second When the water level drops below 3m or the design requirements, remove the light well point pipes in the light well plastic row for the second time of tapping, and the second time of tapping is also 4.5m The square points are arranged in a plum blossom shape with the first ramming point (or according to the geological conditions and design requirements). The heavy ramming is carried out for so many times to achieve the required bearing capacity. After multiple rounds of light wells, plastic drainage points are dewatered. , After multiple rounds of point ramming, the last full ramming, the full ramming construction with no leakage and no upturning is the obvious effect. It can also be adjusted according to the design or test ramming situation. The standard of dynamic ramming hammer is controlled by the number of ramming strokes, and the ramming weight of the last two consecutive strokes is not more than 10cm.
[0049] The lifting height of the rammer in construction is calculated according to the following calculation formula:
[0050] The hoisting height H value is: H=M/T+h+a-b
[0051] among them:
[0052] M-Design for energy
[0053] T-hammer weight
[0054] h——The height from the lifting point of the tamper to the hammer surface
[0055] a——surplus parameter, take 0.2;
[0056] b——1/2 designed ram depth, 0.75.
[0057] The dynamic compaction machine mainly adopts crawler crane, and spare auxiliary gantry according to the actual situation on site.
[0058] According to the requirements of soft foundation reinforcement, the soft soil foundation to be treated can be strengthened multiple times according to the above method to make it meet the required bearing capacity requirements. During the construction process of dynamic compaction, attention should be paid to the dissipation of excess pore pressure. % And above, the next round of construction can be carried out; after multiple rounds of point ramming, the last full ramming can be carried out. During the construction period, the peripheral pipes should be kept and continue to dewater until the final dynamic compaction is completed before the peripheral well point pipes can be removed.
[0059] After the full compaction is over, after the pore pressure has dissipated to more than 90%, the road and site structure can be entered for construction.
[0060] Dynamic consolidation can also use construction techniques such as vibration rolling or impact rolling.
