Silt soil has the characteristics of very low strength, large compressibility, poor water permeability, thixotropy and rheological property Foundation treatmentIn, there will be low bearing capacity, slow strength growth, easy deformation and uneven after loading, large deformation rate and long stability time, which will have adverse effects on the building. Therefore, in the foundation treatment, it is necessary to select appropriate foundation treatment technology for silt soil to ensure the quality of the project. The following are five common methods of silt soft soil foundation treatment:
1, the pile foundation
When the silt layer is thick and it is difficult to conduct deep treatment in a large area, piling can be used to reinforce the treatment. In the early stage, cement and soil mixing pile, sand and stone pile and wood pile were mostly used. Due to their own problems, these three kinds of piles are rarely used at present. And reinforced concrete precast pile has been widely used because of its strong bearing capacity, cost saving, quality assurance, fast construction speed and other characteristics.
This method is suitable for THE shallow treatment of silt, silty soil, collapsible loess, plain fill soil, miscellaneous fill soil, dark ditch, dark pond, etc. The function of the filling method is to increase the bearing capacity of the bearing layer, improve the compressibility of the soil, and reduce the deformation of the foundation. When the soft soil is thin, all can be dug out; When the soft soil is thick, it can be partially excavated. Fill soil can be sand, gravel, plain soil, etc. When the silt layer thickness is relatively thin, the silt layer can also be used to replace sand loam, gray soil, coarse sand, cement soil or caisson foundation for foundation treatment. In view of the fact that sand exchange is not good for seepage control and the project cost is high, the local materials should be generally used to replace the soil. The soil exchange method should be backfilled with the soil with good compaction characteristics and compacted or rammed to form a good bearing layer, so as to change the bearing capacity characteristics of the foundation, improve the anti-deformation and stability ability. Attention should be paid to the stability of the pit side during construction, to ensure the quality of the filler, and the filler should be tamped in layers.
3, the grouting method
The method uses air pressure, hydraulic pressure or electrochemical principle to inject some solidified slurry into the foundation medium or the gap between the building and the foundation. Grouting slurry can be cement slurry, cement mortar, clay cement slurry, clay slurry and various chemical slurry materials such as polyurethane, lignin, silicate and so on. Grouting method has obvious effect on strengthening silt soft soil foundation. The principle of high pressure rotary grouting is to form soil-cement friction pile in the sluice foundation to improve the bearing capacity of the foundation and control the settlement.
4, cement mixing method
This method is a new method for strengthening saturated soft soil foundation. It is the use of cement, lime and other materials as the main agent of curing agent, through the special mixing machinery, in the depth of the foundation will be soft soil and curing agent forced stirring, the use of curing agent and soft soil produced between a series of physical - chemical reactions, so that the soft soil hard formed with overall stability and a certain strength of high quality composite foundation. The method can improve the allowable bearing capacity of the silt foundation, reduce the settlement of the foundation, and improve the resistance to vibration liquefaction. This method has the advantages of fast construction speed, little vibration, no noise and no pollution.
5, caisson foundation method
In the design of the bottom surface of the building on the elevation of the first section pouring, and then dig the earth in the well, so that the well body depends on its own weight to overcome the friction resistance of the wall of the well to sink. Therefore, the height of caisson pouring should be determined according to the soil quality of the foundation and the subsidence speed controlled by the requirements. Caisson foundation has the same function as pile foundation, which is beneficial to prevent seepage deformation of foundation, but it is greatly affected by groundwater during construction.
Selection of silt soft soil layer Foundation treatmentMethods should be selected according to the advantages and disadvantages of the above methods, and combined with the local geological characteristics.
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