| After the excavation of Zhu Ran’s tomb,due to changes in the surrounding terrain and topography,the original groundwater balance system was disrupted,resulting in long-term accumulation of water in the tomb chamber,severe weathering and cracking of the tomb brick and soil,and the growth of moss on the surface of the tomb brick.The main reasons for the water immersion of Zhu Ran’s tomb are the shallow burial of the tomb,the infiltration of surface rainfall and the high groundwater level in the the Middle and Lower Yangtze Valley Plain.Under the long-term dry wet cycle,the soil at the Zhuran Tomb site undergoes repeated expansion and contraction deformation,gradually forming clay aggregates and pores between them.In order to reveal the saturated unsaturated seepage characteristics of the soil at the Zhuran Tomb site,this paper takes the pore size distribution of the site soil as the starting point,measures the pore size distribution of clay particles,conducts tests on the soil water characteristic curve and saturated permeability coefficient of the remolded soil at different dry densities of the site;Studied a prediction method for saturated permeability coefficient based on pore ratio and characteristic pore size,considering the full pore size distribution of agglomerate pores and intergranular pores;Predicted the soil water characteristic curve and unsaturated permeability function within the full suction range.This thesis takes four drilling or corridor excavation soil samples from the Zhuran Tomb Site in Ma’anshan City,Anhui Province as the research object,and explores the saturated unsaturated permeability characteristics of the Zhuran Tomb Site soil under different dry densities.In order to explore the permeability characteristics of the soil at the Zhuran Tomb site,this article used a self-developed high-pressure saturated permeability meter to measure the saturated permeability coefficient of the site’s cohesive soil,a self-developed volume pressure plate meter to measure the soil water characteristic curve of the site’s soil,and a nitrogen adsorption method to measure the pore size distribution of the site’s clay particles.Through the analysis of experimental data,a comparative study was conducted on the prediction and comparison of saturated permeability coefficient,unsaturated soil water characteristic curve,and permeability function.The main content and conclusions of this article are as follows:(1)Characteristics of pore size distribution in the soil of Zhuran Tomb Site(a)By using the specific surface area and pore size analyzer of the school’s analysis and testing center,the pore structure of clay particles at various points of the Zhu Ran tomb soil sample was investigated.The pore size data of the Zhu Ran tomb soil sample was obtained,and the isothermal adsorption curve,pore size distribution PSD curve,and pore size cumulative distribution curve were plotted.The clay particles are mainly mesoporous(2-50nm)and macroporous(50-660nm)is minor.According to the theory of unsaturated soil capillary management,the characteristic pore size is converted into matrix suction,and the relationship between matrix suction and saturation is obtained.According to Poisson’s law,the permeability is linked to the equivalent flow rate through the cross-section to obtain saturated permeability,where the capillary pore size represents a certain characteristic pore size.(b)By using a pressure plate instrument to measure the soil water characteristic curve of the reshaped site soil,and based on the theory of unsaturated soil capillary management,the measured matrix suction is converted into the equivalent pore size of intergranular pores.Combined with the measured particle size distribution,a full pore size distribution can be established.(2)A Study on the Saturated Permeability Characteristics of Zhu Ran Tomb(a)The saturated permeability coefficient of soil samples at various points in the Zhuran Tomb was measured using a self-developed high-pressure saturated permeability meter,and the law of gradually decreasing saturated permeability coefficient of Zhuran Tomb soil samples with increasing dry density was obtained.The saturated permeability coefficient of remolded soil samples from the Zhuran Tomb was also measured under different dry wet cycles.(b)The improved version of Chapius,which is more suitable for the cohesive soil sample of Zhuran Tomb,was obtained through the traditional empirical formula K-C fitting,and the fitted saturation permeability coefficients of each point were ultimately obtained.(c)The saturated permeability coefficient of soil samples at various points of Zhuran Tomb was predicted using the method of pore size distribution,and compared with traditional empirical formula prediction methods.A more suitable saturated permeability coefficient prediction method based on pore ratio and characteristic pore size was proposed for Zhuran Tomb cohesive soil.(3)Study on Unsaturated Permeability Characteristics of Zhu Ran Tomb(a)The soil water characteristic curve test was conducted on three initial dry density soil samples from Zhuran Tomb using a self-developed volume pressure plate instrument.The higher the initial dry density,the higher the air intake value and the stronger the water holding capacity of the soil samples.(b)After fitting the measured SWCC data using three classic models,the FX model that is most suitable for the soil sample of Zhuran Tomb was obtained for fitting.Finally,the fitted data was calculated as an unsaturated permeability function using the statistical model CCG model.(c)The soil water characteristic curves of various points in the Zhuran Tomb were predicted using the method of pore size distribution.Combined with the measured soil water characteristic curves in the low suction section,the soil water characteristic curve in the full suction range was obtained,and then the unsaturated permeability function was predicted from the soil water characteristic curve. |
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