Experimental Study On Soil And Water Coupling Response To Drainage And Recharge

With the accelerating process of urbanization and the excessive exploration of groundwater resources,land subsidence has become an increasingly serious geological disaster,and this not only brings out great loss to the people's life and asset,but also hinders the urban sustainable development.Based on the land subsidence characteristics of Suzhou-Wuxi-Changzhou area,the research uses distributed fiber optical sensing(DFOS)technology in laboratory model tests to study the characteristics of soil water content-deformation coupling during drainage and recharge,and the result reveals the soil water content-deformation coupling rule.The paper achieved the following results:(1)This paper summarizes the research status,current monitoring technology and its deficiency,analyzes the main cause and hazard of land subsidence,and also introduces the research methods and principle of fiber optical sensing technology.(2)Designed a small-scale sand-clay interbed model box.Developed two kinds of special sensing cables,such as the strain sensing fiber optic cable and the carbon fiber heating cable,which were suitable for the indoor strain test and the water-field monitoring.(3)The laboratory model monitoring scheme of drainage and recharge process is designed and implemented,including optical fiber monitoring scheme,layered settlement monitoring,water field monitoring by carbon fiber heating cable,and water level tube monitoring.(4)According to the strain test results,the DFOS technologies have significant advantages that can achieve distributed,sensitive and precise stress-field information comparing to the traditional step branch marks.When drainage or recharge,soil layers show compression or rebound with the water content decreases or increases,and the most compression and rebound concentrated in the clay layer.(5)The monitoring result of water content indicates that soil layers are compressed during drainage and rebound during recharge.The deformation of sand layer is synchronous with water content changes,while that of clay layer is slightly lagging behind the water content changes.(6)The tests indicate that the deformation of sand layer is synchronous with water content changes,while that of clay layer is slightly lagging behind the water content changes.And the deformation of clay layer can be divided into primary consolidation and secondary consolidation.