1. Characteristics of Underground Continuous Walls An underground continuous wall is constructed using specialized excavation equipment. The process involves excavating a slot-shaped hole along the perimeter of a foundation or underground structure to specified dimensions, followed by installing steel reinforcement cages and pouring concrete. These interconnected slabs form a reinforced concrete wall that serves as an effective support structure in foundation pit construction.

Underground continuous wall support systems provide both soil retention and waterproofing. Depending on excavation depth, they can be designed as cantilever structures or reinforced with soil layer anchors and internal supports. These systems may even serve as permanent underground exterior walls for buildings. Featuring high rigidity and structural integrity, they minimize deformation in surrounding foundations caused by excavation work, offering superior safety guarantees for adjacent structures compared to other support methods. The system adapts well to diverse soil types with no inherent limitations. While currently lacking depth restrictions under proper support conditions, its relatively high construction costs remain a notable drawback.

2. Underground continuous walls have been universally recognized as the optimal retaining structure for deep foundation pit engineering in practical applications. They demonstrate the following significant advantages: Construction features low noise and vibration, minimizing environmental impact; The continuous wall exhibits high rigidity and structural integrity, ensuring enhanced safety during excavation with minimal deformation of support structures; The wall body demonstrates excellent impermeability, reducing external effects during dewatering; It can serve as exterior walls for basement structures and be integrated with the reverse construction method to shorten project duration and reduce costs. However, challenges include soil disposal and slurry treatment, as well as potential wall collapse and leakage in silty clay strata, necessitating appropriate measures to ensure construction quality.

3. The application conditions for underground continuous walls are as follows: Due to construction machinery limitations, the thickness of these walls follows fixed modular specifications, making it impossible to adjust pile diameter or stiffness as flexibly as cast-in-place piles. Therefore, underground continuous walls only demonstrate their economic advantages and unique benefits when used in specific depth foundation pit projects or under special circumstances. The selection of underground continuous walls must undergo technical and economic evaluations, and should only be adopted when proven economically viable through comprehensive analysis.

4. Under normal circumstances, the underground continuous wall is suitable for the following conditions of foundation pit engineering: deep foundation pit projects where excavation depth generally exceeds 10m to achieve better cost-effectiveness; projects with adjacent structures requiring high protection standards and stringent deformation/waterproofing requirements for the foundation pit itself; projects with limited space within the site where the basement exterior wall is extremely close to the red line, making other retaining forms unsuitable for maintaining construction operation space; projects where the retaining structure also serves as part of the main structure with strict waterproofing and seepage resistance requirements; projects using reverse construction method where simultaneous above-ground and underground construction is typically implemented using underground continuous walls as retaining walls; and in ultra-deep foundation pits (e.g., 20-30m deep) where other retaining structures fail to meet requirements, underground continuous walls are commonly employed as support.