The Experimental Investigations Of Polypropylene Geotextile Bags In The Treatment Technology Of Seepage Failure Happened In North Of Shaanxi Check DAM

Check dam is one of an important water and soil conservation project in the comprehensive management of small watershed,It not only can increase the area of arable land and improve agricultural productivity,but also can prevent soil erosion.Because of the lack of sand,stone construction and funds in the last century 70 to 80 s,Jingbian and Dingbian area in Northern of Shaanxi built check dams without the vast majority of filter material,resulting in check dam seepage failure and have become dangerous dams,this problem has not been solved,serious security risks for local check dam engineering.Seepage failure had been happened after the dam has become an important problem to restrict the local check dam construction.Based on the dam soil silty loam in Jingbian Gao Gou County of Yulin city in Shaanxi Province as the research object,through the penetration of the original dam outdoor simulation seepage failure phenomenon and process,and using polypropylene geotextile bags filled with soil as a filter to compare the impact of the permeability time and phreatic line.Studying microstructure and pore characteristics of soil sample after dam seepage failure by scanning electron microscopy,Analysising particle sizer of sediment grading of seepage failure in the process of by Malvin laser,Analysis control effect of seepage failure with polypropylene geotextile bags,It can provide theoretical basis and technical support for reinforcement to check dam in North Shaanxi Jingbing region which has been seepaged failure,the research has important practical significance of the study.The main conclusions of this paper are:(1)The results of the conventional soil test for the dam materialThe test results show that the soil sample belongs to medium silt loam soil,and the soil sample is low liquid limit clay.Soil particle size distribution is not uniform,the uniformity coefficient CU=6.12,CC=0.90,The conditions of CU >5 and CC = 1 ~ 3 can not meet at the same time,so it belongs to bad gradation soil samples,soil pore larger between soil particles can be smaller particles more easily through easy to cause the seepage failure in the seepage effect.(2)The results of the basic properties of polypropylene geotextile bagsThe test results show that the polypropylene geotextile bags can better combine with sand soil,and ensure the stability of the whole bag body,on the other hand,it has great tensile and tear resistance.With the bag body aperture is small,easy to flow through,but the soil particles are not easy to pass,so polypropylene geotextile bags are suitable for filter material as the check dam to prevent seepage failure.(3)The results of seepage failure simulation test after the dam1)With seepage failure occurs,the water level height in all parts of the original soil dam gradually increased to a certain value and be stabilized,now the current area of the soil is saturated,the dam water level height were decreasing from the dam front to dam behind.2)Because the polypropylene geotextile bags body size only allows water and small soil particles to flow,so the polypropylene geotextile bags filled with soil as a filter in the prevention of seepage failure,can slow down the rate of water level height increased in all parts of the dam and reduce the maximum height of the water level height,Seepage failure happened in the dam is relatively difficult.On the other hand,the excess water can be discharged out of the dam body,reduce the phreatic line,slow down the occurrence of seepage damage.3)The seepage failure process of the dam body can be divided into three stages: the surface wetting stage of the dam slope,the occurrence and development stage of the seepage damage,and the seepage damage stage.And the failure process and the phenomenon of two simulation dam is similar,but the three stages of the polypropylene geotextile bags filled with soil as the check dam filter the occurrence time is later than the original check dam and sediment silt is also less,indicating that polypropylene geotextile bags can not really solve the seepage failure problem,but to a certain extent can retard the occurrence time and scale of the destruction of seepage failure.4)Seepage flow with seepage failure showed a linear growth trend of the two simulated dams,and growth range is more and more larger,which before increased slowly,but later significantly increased until the dam is destroyed;polypropylene geotextile bags dam seepage failure time is longer than the original dam;the effect of seepage of the original check dam is far worse than the polypropylene geotextile bags filter of the check dam.(4)The results of microscopic research of seepage failure specimen1)The soil porosity and average pore diameter of the soil samples which is below the phreatic line is larger than the original soil dam material and other parts of the soil sample,the average particle diameter is litter than the original soil and other soil dam site is small,and the variation rule of pore roundness and particle size roundness is not obvious.The porosity of the bottom of the soil gradually decrease from the check dam before to dam behind dam,The increases degree of porosity of he polypropylene geotextile bags as the filter of the dam is less than the original check dam.2)The sediment particles distribution interval is mainly [20?m,100?m] of raw check dam soil material and two check dams,through the distribution again of particles in the seepage failure process of original check dam,fine grain soil and some skeleton big particles are easily lost.The polypropylene geotextile bags on the one hand to play a role in preventing the loss of larger particles,on the other hand,a certain extent also inhibited the loss of small particles of soil to ensure the stability of the dam.