Research On Geotextile Envelope For Subsurface Drainage In Coastal Reclamation Area Of Jiangsu,China

The soil salt content of agricultural land in Jiangsu coastal reclamation area is high,and different soil improvement goals need to be achieved through drainage and salt washing measures to meet the requirements of agricultural production,and the subsurface drainage technology is one of the important means of soil improvement.In order to ensure the stable operation of the subsurface drainage under the soil of Jiangsu coastal mudflats for a long time,it is necessary to screen the geotextile envelope material suitable for the local soil.This paper adopts a combination of long-term indoor experiments and theoretical calculations to screen out geotextile envelope suitable for local soils,find out the key factors affecting the performance of geotextile,and analyze the applicability of existing geotextile selection criteria and propose improvements to provide theoretical and technical support for the screening of geotextile envelope for subsurface drainage in areas with poor soil structure.The research results obtained in the paper are as follows.(1)When geotextiles were used in soils with 4.2%clay particles,the ratio of geotextile fraction to overall permeability was around 40.0%,and the average blockage rate and average loss of geotextiles were 29.0%and 1.34 g.In soils with 0.3%clay particles,these figures were 120.0%,11.9%and 0.12 g.The performance of geotextiles in different soil textures is quite different.Compared with the soil with fine soil texture,the same geotextile performs better when used in the soil with coarse soil texture,and all performance indexes are at a higher level.The performance of different geotextiles is quite different.The geotextile G1(O90=227?m)with the largest aperture has the worst soil retention effect,with an average loss of 0.75 g,and the geotextile G5(O90=105?m)with the smallest aperture has the best soil retention effect,with an average loss of 0.53g.(2)The soil factor and geotextile factor have different degrees of influence on the permeability,soil retention effect and anti-blocking ability of geotextile cover filter media.The effect of soil retention of geotextile is relatively influenced by the pore size of geotextile,and the pore size ratio can effectively judge the effect of soil retention of geotextile;the blockage condition of geotextile is more complicated,and the blockage degree of geotextile cannot be effectively judged by geotextile factor and soil factor only.(3)In the screening of geotextiles,the existing criteria for selecting the permeability of geotextiles are precise and effective,and their size can reflect the permeability of geotextiles,but the recommended lower limit value should be enlarged appropriately;the pore size ratio to judge the soil retention effect of geotextiles is effective but imprecise,and the recommended upper limit value of the existing criteria is not a good evaluation of the soil retention effect of geotextiles,and the recommended value of pore size ratio O90/d90 is between 0.8 and 2.5;the gradient ratio to judge the blockage condition of geotextiles is not a good evaluation of the soil retention effect of geotextiles due to the shortcomings of the experimental principle.The pore size ratio O90/d90 is suggested to be between 0.8?2.5;the gradient ratio is used to judge the blockage condition of geotextile,in addition to the problem of the suggested value size,the shortcomings of the experimental principle also lead to the gradient ratio not being able to judge the blockage condition of geotextile well.