| | Method | Advantage | Shortcoming |
| | Dynamic compaction | (1) The dynamic compaction method is applicable to the treatment of gravel soil, silty soil, and cohesive soil with low saturation of sandy soil, collapsible loess plain fill, and miscellaneous fill. Especially for the treatment of collapsible loess, the practice has proved to be effective and reliable.
(2) It exerts great impact energy on the foundation, and the general energy is 1000 kN m∼8 000 kN. m. The shock wave and dynamic stress generated in the foundation can improve the strength of the foundation, reduce the compressibility of the soil, and eliminate the collapsibility of the collapsible loess.
(3) Relative excavation and replacement can reduce the area of arable land occupied by spoil; reduce the amount of sand and gravel; compared with other soft soil subgrade treatment methods, the cost is low, the reinforcement effect is obvious, the construction period is short, and the cost is low. | (1) The reinforcement depth should not exceed 7 m. It has certain limitations.
(2) The magnitude and dissipation speed of pore water pressure depends on the level of groundwater level and the permeability of the soil, which limit the construction period.
(3) The noise and vibration are large, and it is not suitable for use in densely populated cities and residential areas. |
| | Vacuum preloading method | (1) In addition to vertical compression, the soil will also be accompanied by lateral contraction during the reinforcement process, which will not cause lateral extrusion, making it especially suitable for the reinforcement of super-soft soil foundations.
(2) Generally, the vacuum degree under the membrane can reach 600 mmhg, and the equivalent load is 80 kPa, which is about equivalent to a 4.5 m soil load; the vacuum preloading load can be overlapped with the surcharge preloading. When a preloading reinforcement load greater than 80 kPa is required, it can be used simultaneously with the surcharge preloading method. The preloading load exceeding 80 kPa is supplemented by the surcharge preloading.
(3) Vacuum preloading load will not cause foundation instability, so it is not necessary to control the loading rate during construction. The load can be applied quickly at one time, with fast reinforcement speed and a short construction period.
(4) Construction machines and equipment are simple and easy to operate; convenient for construction, high operation efficiency, low reinforcement cost, suitable for large-scale foundation reinforcement, easy to promote, and apply.
(5) It does not need to load materials vigorously, which can avoid the transportation tension, turnover difficulties and construction interference caused by the transportation of materials; no noise, vibration, and environmental pollution during construction.
(6) Suitable for foundation reinforcement in narrow sections and near slopes. | (1) Sufficient and continuous power supply is required: the reinforcement time should not be too long, otherwise, the reinforcement cost may be higher than the surcharge preloading of the same load.
(2) In the process of vacuum preloading reinforcement, horizontal deformation will occur around the reinforcement area to the inside of the reinforcement area, and cracks often occur around 10 m away from the edge of the reinforcement area. Therefore, during construction near buildings, attention should be paid to the impact of foundation horizontal deformation on the original buildings during vacuum pumping. | | Vibroflotation method | (1) Reduce the settlement, form a composite foundation through the replacement principle of gravel pile, and greatly improve the bearing capacity and integrity of the foundation.
(2) Eliminate liquefaction, and eliminate the liquefiable sand layer through the vibration compaction principle.
(3) To improve the strength of foundation soil, the gravel pile is used as the vertical drainage channel of the foundation to squeeze and discharge the water in the saturated soft clay void, so that the foundation will gradually undergo consolidation deformation under the gradual action of the upper load, and finally improve the strength of foundation soil. | Gravel, electricity, water, and other materials are used in large amounts, and it is difficult to discharge sewage, especially in the process of vibroflotation. |
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