| The capillary barrier is the impervious method applied to landfill for preventing the rainwater seep in the rubbish.The pollution fluid could pollute the underground water and surroundings though the migrating.this paper put forward a new structure of the capillary barrier called the capillary barrier with pumping effect area.For the research of the impervious mechanism and characteristic,do the indoor test and theoretical analysis.At first,do the research of the effect on compactness of swcc.Using the wide grade of weathered soil of granite as the test soil.To get the test data of the swcc of different compactness soil,we use the filter paper method and WP4C.The results show:with the compactness increasing,the air entry value increasing.There is the liner relationship between compactness and logarithm of air entry value.It is little effect on the compactness for swcc at middle and residual suction segment.The results also show:with the saturation decreasing,the osmotic suction is increasing.at the low saturation,the osmotic suction increased fast even to several thousand kpa than theoretical calculation,the physical mechanism may be the effect of bound water in the low saturation segment,in high saturation segment,the bound water is low proportion of water in soil,it is little effect on the osmotic suction,but with the saturation get lower,the proportion of the bound water in soil get more high,the effect of the bound water on the osmotic suction is highlighted,put forward the theoritical formula of osmotic suction considering the bound water content.Form the swcc of the different compactness soil,we conducted the soil column model test.The wetting front matched the changing of the water content sensor.For the soil,the more compacted,the lower velocity of the wetting front.Using the test data to get the permeability coefficient function by wetting front advancing method,the results show that the compactness of soil has the very great impact on the segment of the low suction.For the rapid changing segment of suction and permeability,the compactness has little effect on permeability coefficient function.To study the applicability of the wetting front advancing method by numerical simulation for guiding the design and measuring of indoor test,we choose the three types of special soil:clay,sand and gravel soil.The results show:the study expand the wetting front observed by "eyes",getting any water content that is higer than intial water content as wetting front is ok.For the changing curve of the water content versus the time of rainfall seeping about monitoring section in soil column,the wetting front method is only suitable for the first increasing segment of the curve.The number of sensors and the spacing of sensors along the soil column have little effect on the result ’of the wetting front advancing method,so for indoor model soil column test,the height of the soil column is 50cm suggested,3 sensors could be ok along the height direction.The fitting function of the wetting front advancing position vs time is most suitable as polynomial function.For maximum range of permeability coefficient function,we must choose the dry soil for test and get the data of the highest section of sensors in soil column,the rainfall intensity could be closed to saturated permeability coefficient.For clay,sand and gravel soil,the wetting front advancing method of clay is the highest precision.In allowable error,we could use the wetting front advancing method to get the permeability coefficient function of the three types of soil.Based on the indoor soil column model test of capillary barrier in one paper,here the result by the numerical simulation method proves the calculation model in her paper.Further,do the work of optimizing the calculation model.The main structure of the capillary barrier with pumping area includes:upper fine soil layer,lower coarse soil layer and side pumping soil layer.This paper get the theoretical analysis of the requirement of the pumping effect.Also,from the indoor model test of the capillary barrier with pumping area in this paper,we get that the width of pumping area is not the import factor to improve the pumping effect of the pumping area,the permeability of the soil of the pumping area is the key factor.Based on the test data,we put forward the design law of the capillary barrier with pumping area,then use this law to define the design parameter for four city in typical climate area. |
