Development Of Unsaturated Soil Column Test Device And Experimental Study On Parameters Of Capillary Barriers

Capillary barrier is a new form of landfill final cover system.Its seepage mechanism,calculation model,design parameters are need to be further studied.In this paper,in order to study the infiltration behavior of capillary block,conventional capillary block type soil column experimental apparatus and the one with suction force were developed.Rainfall infiltration experiment of uniform soil column,capillary barrier soil column,capillary barrier soil column with suction effects were carried out with the newly developed soil column experimental apparatus.Experimental results demonstrate that:(1)The newly developed conventional capillary block coating soil column experimental device and the pumping experiment are designed with reasonable working condition and can meet the needs of the study of the infiltration behavior of the capillary block.(2)This research improves the wetting front forward method.It is found that the visible wetting front by the naked eye is not a necessary condition for the wetting front forward method,it is feasible to identify the wetting front by the sensor,and the calculation accuracy satisfies the requirement of the measurement of the unsaturated permeability coefficient.This improvement breaks through the limitations of the original wet front approach in relying on the naked eye to observe the wet front,greatly expanding the scope of this method,and more convenient and accurate.(3)The breakdown time of the capillary block is related to the thickness of fine-grained soil,the initial water content of fine-grained soil and the intensity of rainfall,and linearity,linearity and power function are found between them respectively.(4)Based on the experimental data,a simplified calculation model of storage capacity of fine soil layer and the Interface breakdown time of capillary barriers was established.The calculated results are in agreement with the experimental results.(5)Based on the calculation model of storage capacity of fine soil layer and the Interface breakdown time of capillary barriers,several design principles are put forward for the design of fine-grained soil layers of capillary barriers;and specific parameter design is given for four representative cases of the humid areas,semi-humid areas,arid areas and semi-arid areas respectively.(6)A comparative experiment was conducted on the capillary block with suction layer and without suction layer.It is proved that the fine grained soil layer on the side of the coarse soil layer of the capillary block can play a role in drainage and play a role in delaying the breakdown time.