Research On The Model Test Of Soil Subsidence With Variable Water Pressure

As the acceleration of urbanization and the over use of groundwater, the damage of land subsidence become increasingly serious in our country. It has threatened the local people’s life and property safety and restricts the sustainable development of the city. Especially in Su Zhou, Wu Xi and Chang Zhou area, the land subsidence has caused a huge negative influence in local economy construction. The relevant department spends lots of manpower and material resources controlling land subsidence by recharging groundwater, but it’s principle and evaluation of the effect need for further argument.In this thesis, based on the developmental mechanism and deformation characteristics, using BOTDA which developed quickly in the past dozen years in the model test. The model test of soil subsidence with variable water pressure based on BOTDA was carried out systematically, and the deformation characteristics and mechanism of variable water pressure condition of sand and clay layer was revealed. The results are presented as follows:(1) The actuality and deficiency of the monitoring techniques of land subsidence was discussed. The sensing principle, the main technical performance indicators, technical characteristics, application range of BOTDA optical fiber sensing technology were introduced.(2) Designed the equipments and test procedure of variable level land subsidence model test. Determining the properties of soil model through tests.(3) Design and process special sensing fiber for the measurement of land subsidence and settlement pole,according to the characteristics of land subsidence and the difficulties in land subsidence monitoring with distributed optical fiber sensing technology. Laying the sensing fiber by a special method.(4) Monitoring the deformation of soil with distributed optical fiber sensing technology. Demonstrated the feasibility and found the problems of soil-deformation monitoring by using distributed sensing fiber through comparing with settlement pole’s monitoring results.Provides a new deformation test means for small-size indoor soil deformation model test.(5) Based on the deformation of each soil layer in the test, the deformation situation of each soil layer is analyzed deeply and profoundly, and the mechanism is also explained as well.(6) Through comparing and analyzing the rebound in the recharge stage and the settlement of clay layer in the drainage stage, it is found that the former accounted for only 10%-30% of the latter, indicating the settlement of clay due to the variations of water drainage is not completely reversible, providing a new basis for the evaluation of the life process of ground settlement.