1. Cast-in-place pile row retaining wall

1.1 Separated row piles

Separated row piles are the most commonly used and relatively simple form of cast-in-place pile row retaining wall in engineering. On the outer side of the cast-in-place row piles, a corresponding water-stop curtain can be installed according to the groundwater control requirements of the project.

Applicable scope of separated row piles：Wide applicability to strata, from soft clay to silty sand, gravel, and rock foundation pits; in soft soil strata, generally applicable to foundation pit projects with a depth not greater than 20 m; cantilever single-row pile support is generally applicable to foundation pits with an excavation depth of 5-10 m

Characteristics of separated row piles：Simple construction process, mature technology, easy quality control, and economical cost; low noise, no vibration, nosoil squeezing effect，minimal impact on the surrounding environment during construction; the stiffness of the retaining piles can be flexibly adjusted according to the deformation control requirements of the foundation pit; projects with water-stop requirements require an additional water-stop curtain

1.2   Interlocking row piles

Sometimes, due to narrow sites and other reasons, row piles and a water-stop curtain cannot be installed at the same time. In such cases, an interlocking form between piles can be adopted to form an interlocking row pile retaining wall that serves as a water barrier. Plain concrete piles are constructed first, followed by reinforced concrete piles.

Applicable scope of interlocking row piles：Soft soil areas with silt, running sand, and abundant groundwater; conditions where water stopping by mixing piles or jet grouting piles cannot be performed in gravel and other soil layers; applicable to foundation pits with high environmental protection requirements where adjacent buildings and structures are sensitive to dewatering and ground settlement; conditions where the site is narrow and row piles and a water-stop curtain cannot be installed at the same time

Characteristics of interlocking row piles：The load-bearing structure and the water-stop structure are integrated, occupying a small space; relatively high overall stiffness and good waterproof performance; fast construction speed and low project cost (varies by region); dry-hole operation is possible during construction, with no need to discharge mud, and the mechanical equipment has low noise and little vibration, causing little environmental pollution; high requirements for pile verticality, and relatively high construction difficulty

1.3   Cantilever double-row piles

To increase the overall bending stiffness and lateral displacement resistance of row piles, the piles can be arranged in front and rear double rows, and the top capping beams of the front and rear rows are connected by transverse connecting beams to form a double-row portal-type retaining structure.

Applicable scope of cantilever double-row piles：Applicable to conditions where the site space is relatively sufficient, the excavation depth is relatively deep, the deformation control requirements are relatively high, and anchor rods and internal bracing cannot be installed; applicable to foundation pits with an excavation depth not exceeding 12 m; not suitable when there is a relatively thick soft soil layer in the foundation pit; local slope cutting at the top of the slope can be carried out according to actual conditions

Characteristics of cantilever double-row piles:Large bending stiffness, simple construction process, mature technology, and easy quality control; compared with bracedretaining structures，it can serve as a self-standing cantilever support structure, with a short construction period and relatively economical cost when the foundation pit area is large; the retaining body occupies a large space; when there is a water-stop requirement, an additional water-stop curtain is required

2 、 Steel section cement-soil mixing wall

Applicable scope of steel section cement-soil mixing wall：Applicable to a wide range of soil layers, from cohesive soil to sandy soil, from soft soil to relatively hard and relatively dense sandy soil, and even in strata containing sand and gravel, construction can be carried out after appropriate treatment; in soft soil areas, generally used for foundation pits with an excavation depth not greater than 13 m; applicable to construction sites

that are narrow, or when the distance to the land boundary red line, buildings, etc. is relatively short, and the system of row piles combined with a water-stop curtain cannot meet the space requirements of the foundation pit; the stiffness of the steel section cement-soil mixing wall is relatively small, and the deformation is relatively large, so it should be selected with caution for projects with high requirements for surrounding environmental protection; when the surrounding environment of the foundation pit is relatively sensitive to changes in groundwater level, and most of the range of the mixing pile body consists of sand (silty) soil and other soil layers with strong permeability, it should be selected with caution

Characteristics of steel section cement-soil mixing wall

The load-bearing structure and the water-stop curtain are integrated, and the retaining body occupies a small space; the construction of the retaining body has little impact on the surrounding environment; by adopting the socketed one-hole construction, completely seamless connection between adjacent piles is achieved, and the wall body has good seepage resistance; the construction process of the triaxial cement-soil mixing pile does not require recovery and treatment of mud, and the steel sections can be recovered after the foundation pit construction is completed, which is environmentally friendly and energy-saving;

the process is simple, the pile formation speed is fast, and the construction period of the retaining body is short; after the basement construction is completed, the steel sections can be pulled out to realize reuse of the steel sections, resulting in good economy; after the steel sections are pulled out, the voids left in the mixing piles need to be backfilled by grouting and other measures; when adjacent to deformation-sensitive buildings and structures, there are relatively high requirements for backfill quality

3、 Steel sheet pile retaining wall

Combined steel sheet pile

4. Reverse-hanging shaft wall method

5. Open caisson