The Impact Of Paralic Stratum In The West Side Of The Pearl River Delta On Excavation Deformation Of Open Cutting Deep Foundation Pit

With a large number of urban infrastructure project design and construction inour country, deep foundation pit engineerings appear constantly. And the deepfoundation pit engineerings nearby rivers and coastal appear the rapid development inrecent years, quantity of engineerings is growing. Because the construction and theexcavation of foundation pit engineering in Paralic stratum is rare, so the formation oftargeted research work of soil engineering properties in this stratum is not ascomprehensive as other strata in the study. To control deformation of foundation pit isthe basis for the safety control of foundation pit engineering, therefore this articlelaunches the study on the impact of Paralic Stratum on excavation deformation ofopen cutting deep foundation pit across the sea, Aimed to explore the degree andmechanism of influence of this stratum on the deformation in the construction of thedeep foundation pit engineerings nearby rivers and coastal, to achieve the purpose ofdeformation control, ensure the safety of engineering. In this paper, the stratigraphiccharacteristics of the Paralic stratum and deformation laws of foundation pit areanalyzed and summarized, combined with field monitoring data the influence of thestratum on deformation of foundation pit in engineering examples are summarized,and the excavation of deformation is simulated by establishing the calculation model.Main work and conclusions are as follows:1. By describing the characteristics of the conventional properties of soil inParalic stratum，summary and analysis the characteristic of soil formation in the studyarea; summarizes the deformation law and mechanism, preliminary judges that thedeformation that apply to the foundation pit engineering in Paralic stratum; focusedanalysis the influence of soil properties on foundation pit deformation, considered the rheology of soil as the key factors.2. Picks on the typical deep foundation pit excavated engineering in Paralicstratum as the object of field experiment, designs the scientific and rational targetedmonitoring plan; through long-term field monitoring and data collection, finds that thetype of the excavation deformation of the structure formation and the soil in Paralicstratum is the combined form, heave of pit bottom is the elastic deformation.3. Choose soft soil model and by using analog software take a numericalsimulation for complex formation structure under excavation in Paralic stratum, findsthat the deformation of retaining structure has obvious asymmetry and theunderground water level change evidently affects the deformation of excavation;determines the numerical simulation method is overall feasible by comparingsimulation results with the measured data.4. Records the process of retaining structure collapse accident of the selectedfoundation pit, and has carried on the preliminary analysis of its geological reasons;finishes the numerical simulation of collapse process from the perspective of thedecrease of strength of soil, finds that when the soil strength decreased to40%of itsoriginal value, the horizontal displacement of the soil at the lateral and bottom of theretaining structure lead to accidents; preliminary judge if the foundation pit in suchstratum has deformation greater than20mm in the short term, then the soil has largepossibility of creep deformation, existing the hidden trouble of collapse accident.5. Explores factors of soil properties influencing the deformation, carries on thecomparative analysis from multiple angles, like the marine silt layer and alluvium inParalic stratum, formation phenomenon, rheological property of soil, soil permeability;analysis and proves that the above elements are in the different degree of deformation.Above research is based on the theoretical study, combining the monitoringdata’s analysis and the numerical simulation. Move forward the study of the impact ofParalic stratum on excavation deformation of open cutting deep foundation pit. Theachievement is full of referential meaning and practical application value in theengineering in this area and other regions with similar geological conditions.