Brief principle:Excavate soft or poor soil to a certain depth and backfill with geotechnical materials of higher shear strength and lower compressibility, such as sand, gravel, mixed slag, etc., to form a double-layer foundation. The cushion can effectively diffuse the foundation stress, improve the bearing capacity of the foundation and reduce settlement.

Applicable scope:Various soft soil foundations

Brief principle:Replace the silt by dumping riprap or tamping backfilled crushed stone to reinforce the foundation; blasting squeezing replacement may also be adopted.

Applicable scope:Silt or silty clay

Brief principle:Use the method of dynamic compaction while filling crushed stone to form crushed stone pier bodies in the foundation; the crushed stone piers, the soil between the piers and the crushed stone cushion form a composite foundation to improve bearing capacity and reduce settlement.

Applicable scope:Silty sandand soft clay foundations

Brief principle:Through mechanical or manual hole formation, add quicklime or quicklime plus other admixtures into the soft foundation; through the water absorption and expansion, heat release and ion exchange of lime, improve the physical and mechanical properties of the pile andsoilto form a lime pile composite foundation, improve bearing capacity and reduce settlement.

Applicable scope:Miscellaneous fill and soft clay foundations

Brief principle:Set drainage channels and a vertical drainage system in the foundation to shorten the consolidation drainage distance of the soil body; the foundation consolidates by drainage under the load of the filled embankment, and after the bearing capacity of the foundation is improved, the settlement is reduced.

Applicable scope:Soft clay, miscellaneous fill, peat soil

Brief principle:The principle is basically the same as the preloading method, except that the preloading load is greater than the design service load. Surcharge preloading can not only reduce post-constructionconsolidation settlementbut also eliminate part of the post-construction secondary consolidation settlement.

Applicable scope:Soft clay, miscellaneous fill, peat soil

Brief principle:Set up a drainage system in the soft clay foundation (same as above), then form an airtight layer on top; through continuous air and water extraction over a long period, a negative pressure zone is formed in the foundation, so that the soft clay consolidates by drainage, achieving the purpose of improving bearing capacity and reducing settlement. It is often used in combination with surcharge preloading.

Applicable scope:Soft clay foundations

Brief principle:By lowering the groundwater level, the stress state of the foundation soil is changed; its effect is like preloading, causing the foundation soil to consolidate by drainage and achieve reinforcement.

Applicable scope:Sandy soil or soft clay foundations with good permeability

Brief principle:Use a deep mixer to mix cement or cement powder with the foundation soil in situ to form cylindrical, grid-shaped or continuous wall-type cement-soil walls, forming a composite foundation to improve bearing capacity and reduce settlement. It is also commonly used to form cement-soil seepage-proof curtains. Deep mixing is divided into two types: slurry spraying mixing and powder spraying mixing.

Applicable scope:Silt and silty soil; when the organic matter content is high, tests are required to determine its applicability

Brief principle:Use special high-pressure jetting machinery to cut the soil body in the foundation through high-pressure jet flow, and replace part of the soil with grout to form cement reinforcement bodies. According to the composition of the jet flow, high-pressure jet grouting includes single-pipe, double-pipe and triple-pipe methods. High-pressure jet grouting can form a composite foundation to improve bearing capacity and reduce settlement.

Applicable scope:Silt and silty soil; when the organic matter content is high, tests are required to determine its applicability

Brief principle:Under grouting pressure, thick grout is injected into the soil layer to form grout bulbs in the foundation soil that squeeze out the surrounding soil. The foundation performance is improved through compaction and replacement. During grouting, the squeezing effect of the grout can produce radial uplifting force, causing the ground surface to heave.

Applicable scope:Commonly used for compressible foundations and cohesive soil foundations with good drainage conditions

Brief principle:Use a tamper weighing 10-40 t falling freely from a height; the foundation soil is densified under the impact force and vibration force of dynamic compaction, which can improve the bearing capacity of the foundation and reduce settlement.

Applicable scope:Foundations such as gravel soil, sand, low-saturation silt and cohesive soil, collapsible loess, miscellaneous fill and plain fill

Brief principle:Use the vibratory driven pipe method, etc., to install gravel piles in the foundation; during pile construction, a compaction effect is produced on the surrounding soil layer. The compacted soil between piles and the dense sand-gravel piles form a sand-gravel pile composite foundation, achieving the purpose of improving bearing capacity and reducing settlement.

Applicable scope：Sand foundations, unsaturated cohesive soil foundations

Brief principle: Lay reinforcing materials (such as geotextiles, geogrids, etc.) in the foundation to form a reinforced cushion, so as to increase the pressure diffusion angle and improvefoundation stability

Applicable scope:Various soft foundations

Brief principle:Install low-strength concrete piles in the foundation to form a composite foundation with the soil between piles, improving the bearing capacity of the foundation and reducing settlement, such asCFG piles

Applicable scope:Various deep soft foundations

Brief principle:Install reinforced concrete piles in the foundation to form a composite foundation with the soil between piles, improving the bearing capacity of the foundation and reducing settlement.

Applicable scope:Various deep soft foundations

Brief principle:Long piles and short piles together with the soil between piles form a composite foundation to improve the bearing capacity of the foundation and reduce settlement. The long piles and short piles may be of the same pile type or different pile types. Usually, long piles use rigid pile types, and short piles use flexible piles or granular material piles.

Applicable scope:Various deep soft foundations