What Factors Should Be Considered for Foundation Pit Dewatering?

To ensure dry construction conditions and prevent the slope from becoming unstable, the following points need to be considered during the construction process:

I. Site Conditions and Architectural Design & Construction Documents

Site conditions制约the development of the precipitation plan, which primarily includes the height, distribution, structure, and distance of existing buildings around the site; underground facilities surrounding the foundation (including water supply and drainage pipes, fiber optic cables, gas supply pipes, etc.); water and drainage channels outward; and power supply situations. Relevant design and construction documents include excavation dimensions and distribution of the foundation pit; requirements for the construction of underground structures. These conditions determine the chosen precipitation methods and specific design and construction plans, as well as the implementation measures to ensure the safety of surrounding buildings and underground facilities.

Geological Conditions

Understanding the stratigraphic column and geological profile, the physical and mechanical properties of the soil and rock layers, groundwater types and burial conditions, hydrogeological conditions, and water quality analysis results, particularly the permeability of soil layers. The permeability coefficient of soil depends on factors such as the formation conditions, particle size distribution, colloidal particle content, and soil structure, thus the permeability coefficients at different depths and orientations within the soil layer of the site vary.

The accuracy of the permeability coefficient calculation directly impacts the selection of the precipitation plan. Due to the complex factors influencing permeability, the values provided in most survey reports are typically laboratory test data, with significant errors. These can only be used for reference during precipitation design. For key projects, on-site pumping tests should be conducted to determine the coefficient.

Section 3: Groundwater Condition on the Site

Groundwater is categorized into two types: phreatic and artesian. Phreatic water is stored between the earth's surface and the first impermeable layer, being a pressureless gravity water that can permeate in all directions. From engineering practice, phreatic water primarily originates from atmospheric precipitation and leaks from broken water supply and drainage pipelines underground, mainly accumulating in the subsurface fill soil and foundations of old buildings that have been eroded and hollowed out.