Abstract
With the continuous development of city construction and development of underground engineering, increasingly large scale, all kinds of super large and deep foundation pit appear constantly, especially in soft soil and high groundwater level area. Due to the leakage problem of the foundation pit engineering, accidents happen. Pit leakage is a common construction defect of construction waterproof curtain, therefore, it is necessary to detect the leakage situation of the foundation pit supporting system in advance, so that the leakage area is treated and prevented in time. In the foundation pit engineering, it is often used to observe the water level changes inside and outside the foundation pit to deduce the approximate area of the foundation pit leakage. Therefore, the use of geophysical methods for leakage detection research has become a breakthrough in solving the problem of leakage of foundation pit. In this paper, variation of groundwater flow around the foundation pit line is discussed when there is leakage of foundation pit system, for instance, leaking water aggregation, intensive regional seepage resistance, resulting in low resistivity of leakage area around the foundation pit of low resistivity. Based on the resistivity imaging technique, the method for detecting the leakage of the foundation pit by detecting the change of resistivity of soil around foundation pit before and after dewatering is presented. It is through two engineering examples show that this method can detect the pit leakage detection results of three-dimensional position, detection results objectively and accurately.
Highlights
With the development of urban construction and the continuous improvement of construction technology, various types of construction and municipal engineering in China have been developing rapidly in recent years, especially the emergence of urban underground works, high-rise buildings and super high-rise buildings represented by underground railways and large transport hubs
The leakage of foundation pit enclosure system will lead to leakage of groundwater around the enclosure system, and the physical properties of the soil will change
The method of detecting the seepage of foundation pit is the characteristic of the change of the flow line of groundwater around the foundation pit and the change of the soil resistivity around the foundation pit
Summary
With the development of urban construction and the continuous improvement of construction technology, various types of construction and municipal engineering in China have been developing rapidly in recent years, especially the emergence of urban underground works, high-rise buildings and super high-rise buildings represented by underground railways and large transport hubs. The excavation depth of the deep foundation pit is getting larger and larger, accompanied by a large number of deep foundation pit projects, especially in soft soil and areas with high underground water level. Because of the leakage problem of foundation pit engineering, accidents often happen. Foundation pit enclosure system is widely used in underground structure construction of high-rise buildings. Most of the foundation pit accidents (domestic and foreign) are related to the leakage of foundation pit retaining system. The leakage of foundation pit enclosure system will lead to leakage of groundwater around the enclosure system, and the physical properties of the soil will change . Using suitable geophysical methods to detect changes in physical properties of soil before and after leakage, the purpose of leakage detection can be achieved. Test becomes dewatering, the streamline falls to the leak point, and the streamline is concentrated (Figure 1 (c), 1 (d))
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