A Study On Influence Of Of Round Gravel Soil Distribution Situation On Water Stop Curtain Construction

Since China’s reform and opening up,with the speeding up of urbanization and the development and utilization of underground space,the deep foundation pit engineering is rapidly developing, the level of design and construction have been obviously improved. However, there are also many problems in the process of development is worth our thinking. For example, in the whole construction process of foundation, the pit engineering accident are still relatively high, and there are about a third of the foundation engineering have arisen the varying degrees quality problems in the early development, even in the construction technology of relatively developed area, it is also hard to avoid. Especially in the strong permeability geological conditions with the rich groundwater, groundwater flow will cause the serious interference to the various construction content of foundation pit engineering, so the selection of construction scheme, construction technology and quality control are particularly important for the smooth completion of foundation pit engineering and the subsequent projects construction.This article through the existing foundation pit project, analysis and research in strong water permeability, the construction technology of the water stop curtain within the scope of round gravel layer, construction quality management and construction scheme optimization. The main work include the following content:(1) Summarize some unfavorable to the construction control of the hydrogeological conditions currently in the process of foundation pit engineering construction (emphasis on the round gravel layer), and the development and research methods of the deep foundation pit of groundwater seepage research, and summarize several common type of water stop curtain and its development process based on years of construction technology development.(2) According the basic condition of this project, state the original design thinking and stop water curtain construction plan, and the reasons that due to geological and construction cause of failure of water stop curtain and to carry out specific analysis on the problem. First of all, according to the geological condition to do the round gravel layer permeability experiments, the experiment mainly includes selecting the river sand which have the similar physical properties with round gravel layer to do the comparative experiments, and separately to do the stone screening of the whole round gravel soil, the sand screening for round gravel soil whose diameter is less than19mm and the sand screening for river sand. Then according to the experimental results, draw2D coordinate to compare and analysis. Secondly, use the engineering software GeoStudio module SEEP/W to simulation analysis the geology construction and the failure of water stop curtain. The analysis includes the influence on seepage of foundation pit, which is caused by the curtain defects existing in the round gravel layer and other layers.(3) According to the theory and software simulation, optimization the water stop curtain construction plan under special geological conditions, such as round gravel layer. Finally sum up the relevant construction quality problem and safeguard measures in construction quality.Based on each work described above, the final conclusions are:(1) Due to the geological conditions where the project is located--the large porosity of the round gravel soil layer and the extremely non-uniform gradation in the particles, the large ones of which are more than the little ones while the latter has more pores to fill, it will lead to the difference of compaction degree, increasing the pores and enlarging the osmosis property and ultimately the flow properties of the underwater passing the pores are strengthened.(2) Because of the large osmotic coefficient in the round gravel soil layer, there are huge perturbation and destruction caused by the underwater, no matter whether it is on the piles-formed process or the deficiencies of the piles themselves. How to deal with this condition should be taken into consideration seriously.(3) An optimization in the machinary and construction technology using water stop curtains are summarized. A new type of material for mixing pile and construction technology are proposed and by these improvement it could make the curtaining method more adaptive to the round gravel soil, which is a kind of special soil in engineering. What’s more, the quality of curtaining method and the effectiveness of stopping water can be guaranteed. Then the illustrations that pointed out where it should be noticed and reinforced during the operation are given from the viewpoints of design and construction respectively, which can provide the subsequent engineering with practical references.