Foundation Pit Support Project for the Xiuzhou District Medical and Health Care Center

Project Overview

The project overview is as follows:

The proposed site is located on a planned road in Jiaxing City. For this project, ±0.000 corresponds to an absolute elevation of +4.15 m. The project includes a two-story basement area, with a foundation pit excavation depth of 9.15 m and a foundation pit perimeter of 668 m (along the bottom boundary line of the pit). Design service life: 2 years.

FCW Five-Axis Cement-Soil Mixing Pile Waterstop Support

A waterstop curtain made of five-axis mixing piles with a diameter of 850 mm is used along the inner edge of the foundation pit.

Foundation Pit Support Plan

Five-Axis Mixing Pile Section

Construction Site Photo

FCW Construction Method

Basic Technical Principles

The non-replacement five-axis cement-soil mixing pile (wall) adopts an upper and lower grouting process to forcibly mix cement with soil in situ, thereby improving mixing uniformity and preventing the stabilized soil from flowing up and down. During mixing and sinking, grout is injected through the lower grouting port; during mixing and rising, grout is injected through the upper grouting port. During the mixing and sinking process, the soil-layer balancing system removes undisturbed soil in advance according to the replacement rate, achieving a balance between the water and earth pressures of the stabilized soil. One down-and-up cycle (two mixing passes synchronized with two grouting passes) completes the construction of one pile wall panel. Construction proceeds by successive overlapping or interlocking until the entire pile wall is completed.

Technical Features

1. The arrangement of five parallel drill rods improves single-operation efficiency and effectively reduces the occurrence of cold joints at overlaps;

2. Grouting through the drill rods allows mixing to be carried out simultaneously with sinking and excavation, improving mixing efficiency;

3. The grout supply system is equipped with variable-frequency motors, allowing manual control of variable grouting at different depths and adjustment of grout volume at any time;

4. The pile frame has a walking-type or crawler-type automatic traveling function, reducing labor intensity and improving operational efficiency;

5. The non-replacement pile-soil mode saves construction time compared with dual-axis mixing piles, costs less than triple-axis mixing piles, and causes little environmental pollution.

6. The drilling depth can reach 45 m (ordinary dual-axis mixing pile rigs can drill only about 18 m).

Scope of Application

It can be used for foundation treatment in water conservancy projects such as sluices and pumping stations (normally consolidated mud and muddy soil, silt, saturated loess, plain fill, cohesive soil, and saturated loose sand without underground rivers, etc.). With scaled application of the technology, it can be used for waterstop curtains of foundation pits in water conservancy projects, trench wall reinforcement for diaphragm walls, support walls (with inserted core materials), soft soil foundation reinforcement, and so on.