Analysis Of Stability Of Laterite Foundation Pit Slope In Hainan

As the construction of Hainan International Tourism Island is carried as the state strategy, the construction of matching infrastructure has been expanded in big scale. Under this situation, it is of certain directive significance for theoretical research and engineering practice to do further study on the engineering properties of the regional laterite produced from magmatic rocks weathering in Hainan, to summarize and analyze the main factors influencing the stability of laterite foundation pit slope as well as to explore the deformation of laterite foundation pit slope in construction process.On the basis of the research on formation mechanism and the main engineering properties of Hainan laterite, the thesis analyzed the main factors influencing laterite slop, calculated the self-stabilizing height of laterite slope, summarized the common foundation pit supporting schemes and appraised their advantages, disadvantages and application scope. Further, the thesis took the foundation pit supporting scheme of the new building of Hainan airlines (as the Haikou landmarks engineering) as an example, systematically analyzed the monitoring results of foundation pit, gave an appraisal of foundation pit supporting scheme and summarized the deformation of laterite foundation pit in construction process. Finally, the thesis gave a prediction of the deformation of laterite foundation by means of grey system theory and explored the feasibility and applicable conditions of GM (1,1) model for predicting the deformation of laterite foundation pit. The main conclusions are as follows:The parent rock types and climates of the Hainan laterite and the Southwest red clay are different. Hainan laterite is produced from magmatic rocks weathering mainly, especially red clay produced from basalt weathering, while red clay at Southwest is mostly produced from carbonate weathering. The two kinds of soil have some similarity of physical mechanics.The thesis, based on the real situation of Hainan, analyzed that water as well as mineral compositions and its structure are the main influencing factors of the stability of laterite foundation pit slope. Because the main structure of Hainan laterite is produced from cementing of free oxide, change of soil moisture effects soil cohesion and stability of foundation pit. If laterite is under desiccation, fracture will caused inside the laterite and the stability of foundation pit slope will be influenced then. The adoption of construction parameters has important influence on maintaining the stability of foundation pit. The calculation results of self-stabilizing height of the vertical slope by means of the Kalman Formulation and Taylor Graphic Method were very similar. The calculation results of self-stabilizing height of the slope indicated that Taylor Graphic Method was comparatively applicable. The self-stabilizing height of laterite slope ranged from 2.3m to 16.9m when the slope angle was between 60°and 90°, the cohesion between 10 kPa and 25kPa and the angle of internal friction between 5°and 25°.The site monitoring data indicated that foundation pit excavation was the leading cause of deformation of soil around foundation and precipitation also influenced the deformation. The deformation would not tend to be stable as soon as completion of excavation. The deformation of the foundation pit enclosure structure and the peripheral soil would be quite obvious during 20 days after completion of excavation. During this period, the monitoring institute should pay close attention to the data of each monitoring item and give a timely feedback. The construction institute should strengthen maintenance of the enclosure structure so as to ensure safety of foundation pit.Grey system theory could be used to predict the deformation of the laterite foundation pit, meanwhile; data and precision of grey model were required to be checked. Furthermore, we need to know that grey prediction is only a semi-quantitative or semi-qualitative analysis method which could not predict the deformation of foundation pit with total accuracy. What we can do is to analyze the deforming tendency of foundation pit with relative accuracy so as to eliminate the possibility of potential destruction.