Study On Moisture Transport Law Of Silt And Seepage Characteristics Of City Wall Considering Clay Content

There are a large number of ancient city wall ruins in Henan,and the walls are mostly built of silt.The high content of powder particles and the low proportion of clay particles result in high porosity.Under rainfall conditions,infiltration is obvious,and the influence depth is large,which may cause collapse of the city wall.In the protection and renovation of city walls,the permeability of walls is often improved by replacing clay,but the research on the influence of clay content on the hydraulic characteristics of silt is not systematic.Therefore,it is of great significance to study silt suction and seepage characteristics under the influence of clay content and put forward some important construction parameters,such as clay content,dry density and thickness of overlying soil,to guide the site repair.Taking the scattered silt of Zhenghan Old City Wall Ruins in Henan Province as the test benchmark,the clay content in silt was adjusted by adding kaolin.The main research contents and results are as follows:(1)The relationship between the saturated water content of the sample and the clay content and dry density was investigated.(2)The variation of matrix suction and total suction of silt with water content under different clay content and dry density was studied by filter paper method.(3)Based on the improved Geo-Expert 1D Column,the influence of clay content on the seepage field of one-dimensional soil column under heavy rain conditions was analyzed.(4)With the increase of clay content,the effect of clay is more on the filling and inlaying of pores.The pore size and area of pores between the particles are significantly reduced,and the adhesion of clay to the surface of the particles is significantly increased.With the increase of dry density,the micro-pore of silt particles gradually transits from large and more to dense and compact.(5)The generalized calculation model of the typical ancient city wall is used to analyze the seepage field changes of the wall body under heavy rain conditions using Midas–GTS NX.(6)Combining macroscopic and microscopic tests and numerical simulation calculations,considering the difficulty and cost effect of site restoration,it is suggested that the silt with 22%clay content after adding kaolin should be used as tamping material in the protection and renovation of city walls,and the dry density should be set at 1.6g/cm~3 and the thickness of the covering soil should be set at 50cm.This will play a good role in improving the impermeability of the soil.