Rainfall in Foundation Pits Construction
Rain is an important climatic factor for geological engineering construction, and its influence on the safety and stability of foundation pit is particularly significant. Rainfall may lead to the accumulation of groundwater and the inflow of water into foundation pit. The inflow water appears not only in the form of surface water flowing from outside, but also from the groundwater in the foundation pit, which may cause massive debris, collapse of foundation pit wall, collapse of internal support and other dangerous disasters.
Foundation pit is divided into two categories according to soil texture: cohesive soil and non-cohesive soil. In the case of non - cohesive soil, if rainfall exceeds a certain amount and the soils infiltration capacity and the surface runoff volume far exceeds the infiltration amount of the soil, the accumulation of surface runoff and the inflow volume of water will increase abruptly. If persist for a long time, the stability of foundation pit may be affected, and a certain amount of displacement and failure may occur. For cohesive soil foundation pit, rainfall might lead to the contraction of cohesive soil, forming a temporary unstable soft layer on the foundation. The soft layer can reduce the bearing capacity of the foundation pit and at the same time increase the surface water pressure, and thus reducing the stability of the foundation pit.
In order to prevent potential safety hazards in foundation pit caused by precipitation, it is necessary to pay attention to the following aspects:
1. Before the excavation of the foundation pit, it is important to choose the rainy season and plan the construction period reasonably to reduce the probability of rainfall during the construction, and the working period should not exceed the prolonged operation during the heavy rain.
2. In the period of rainfall, the personnel entering and leaving the foundation pit and the construction machinery, should reduce the frequency and intensity of activities and reduce the influence of rain on the soil in the foundation pit.
3. It is also important to pay attention to the installation of a precipitation warning system in the foundation pit, which can monitor the weather in real time and make early warning in time.
4. The foundation pit should be screened at both ends and the trench should be surrounded. Boosting up the seepage retaining wall at both ends of the foundation pit will help reduce the inflow of water into the foundation pit.
5. Pay attention to the foundation pit drainage system. When the foundation pit is dug down to a certain depth, it is necessary to install the corresponding drainage measures such as installation of drainage wells and pipe drainage systems.
6. Pay attention to the waterproof measures. In rainy season, the surface should be paved with waterproof material, and the construction joints should be sealed to reduce the inflow of surface runoff into the foundation pit.
7. The foundation pit should be provided with a solid support system and anti-rain measures according to the construction drawing, considering the safety factor of the foundation pit.
Rainfall has a great influence on the safety of foundation pit construction, which should be given enough attention. The construction team of the project should pay attention to the rainfall during the construction period and take corresponding measures in advance to ensure the safe and orderly construction of foundation pit.
