Experimental And Simulation Study On Lateral Anti-seepage Effect Of Vertical Soil Sand Layer In Sunken Lawn

Sunken lawn is one of the technical measures for rainwater utilization in the construction of "sponge city",and it is widely used around urban roads,communities and parks.The designed sunken lawn is used to fully collect rainwater,which increases the time and amount of rainwater infiltration.However,in the northwestern part of China where the geological conditions are mostly flooded collapsible loess,the sunken lawn technology should be sufficient Considering the unfavorable geological conditions,when promoting the application of the "sponge city" technology,the occurrence of geological disasters due to rain seepage should be fully considered.This research is to solve the problem of surrounding building foundation damage caused by the collapse of loess caused by the infiltration of rain and water generated during the construction of sponge cities in collapsible loess areas.In this paper,through the actual detection and analysis of the actual soil in the test device,it is proposed that the vertical soil sand layer structure is set in the sunken lawn system,and the HYDRUS model software is established by measuring and reducing the test data and software verification.Based on the actual rainfall data of Xi'an from 2006 to 2015,the vertical soil sand layer of the sunken lawn was analyzed and studied under the most unfavorable rainfall conditions against the seepage of the sunken lawn under the conditions of different depth,thickness and particle size ratio.As a result,it is proposed to set up the sunken lawn with the vertical soil sand layer,which has the best anti-seepage effect.The main conclusions of the study are as follows:(1)In terms of protection against irregular infiltration of rainwater and accumulated water,and directed infiltration of moisture in soil.Thesunken lawn with a vertical soil-sand layer structure protection system has an obvious effect compared to the ordinarysunken lawn;(2)The simulated water content data at the HYDRUS simulated observation point and the law of the shape of the wet front movement are compared and analyzed with the real-time data of the glass soil box test device with the measured machine.High,the established two-dimensional model,initial conditions,boundary conditions,etc.are suitable for the soil infiltration process of thesunken lawn.You can use HYDRUS-2D / 3D to simulate the infiltration of soil moisture in the sunken lawn in practical applications;(3)Comparative analysis of the anti-seepage effect of the vertical soil sand layer on the ditch-type sunken lawn under the three setting scenarios,and it is obtained that the thickness of the sand layer is 60 cm,the depth is 7m,and the particle size ratio is 2 Has better protection effect;(4)The optimal working conditions selected in the ditch-typesunken lawn cannot completely avoid the observation point below the sensitive water content in the pond-typesunken lawn,but it also produces a significant wetting front and water content reduction effect.When the point is 3.2m away from the bottom of the sand layer,it can cope with the maximum annual rainfall of the pond-like sunken lawn,so that it can avoid below the sensitive water content.