Model Test Of Rainfall Infiltration And Numerical Analysis For Predisintegration Carbonaceous Mudstone Embankment

In Yunnan,Guangxi and other areas,due to the extreme shortage of high quality fillers in the subgrade and the wide distribution of carbonaceous mudstones(CM),so it is inevitable to predisintegrate CM as subgrade fillers.There exists some undesirable characteristics of CM,such as severe slacking deformation and easy disintegration with water and softening.Thus,surface subsidence and slope collapse are most likely to occur when apply CM to practical embankment filling.Therefore,this paper carried out an one-dimensional rainfall infiltration experiment of predisintegration CM and established numerical model to calculate the results,then compared it with the experimental outcome.Under the condition of different rainfall level,the correlation analysis of the seepage characteristics and stability of the predisintegrated CM is conducted based on the experimental results.The main conclusions are as follows:(1)The results of disintegration CM show that its structure and the connection between particles will become more unstable with the drying environment,and it will disintegrate quickly after water absorption.Through X-ray diffraction analysis,it is known that the main components of the CM including montmorillonite,illite and kaolinite,are belong to the hydrophilic clay minerals.The strength of these minerals will decrease rapidly when wet,leading CM gets disintegration and destruction.(2)Apply one-dimensional rainfall infiltration test model designed by our-self to perform seepage test of predisintegration CM under different rainfall conditions,the experiment results indicate that the volumetric water content of the soil near the surface rises first after the rainfall begins,then keeps the same level during a certain rainfall time;the trend of the volumetric water content of the soil in the same vertical section is"rising-stability-rising-stability" and the soil in the middle of the model is"rising-descending-stability-rising-stability" in general with condition of raining but undrain;the volumetric water content of the CM soil keep constant with the condition of draining when raining,and the permeability coefficient corresponding to the soil moisture content is basically the same as the rainfall intensity;(3)A one-dimensional rainfall infiltration numerical model was established by GeoStudio software to simulate one-dimensional rainfall infiltration test of predisintegration CM under the same experimental conditions in the laboratory.The changes of pore water pressure and volume water content were basically consistent with the results obtained from laboratory tests,proving the results of this paper are reasonable and reliable(4)The results of the numerical analysis of the seepage characteristics of the predisintegrated CM under different rainfall conditions show that the increase of the volume water content of the foot position of the embankment is the fastest,the position of the top slope is the slowest under the same rainfall condition.And the slope foot position of the predisintegration CM road embankment is easy to appear a larger saturation phenomenon After a period of rainfall,the volumetric water content of the surface of the embankment remains less fluctuating in a certain range,and the larger the rainfall intensity is,the higher the volumetric water content of the soil surface,which is also verified in the one-dimensional rainfall infiltration test of the CM.(5)The results of the numerical analysis on the stability of the predisintegration CM under the conditions of rainfall show that the rainfall has less influence on the stability of the predisintegrating CM embankment when the rainfall intensity is comparative light.With the increasing of rainfall intensity,the decrease of the stability is increasing.In the initial stage of rainfall,the safety factor of embankment remains unchanged.With the continuous rainfall time,the safety factor of embankment increases first and then decreases,the increase of safety coefficient is smaller.Then the time of rainfall continuously increases,and the safety coefficient of embankment is reduced continuously.After the rain stopped,the safety factor of embankment increased again rapidly.The greater the height of predisintegration CM embankment is,the less rainfall influence on its stability.The higher the slope ratio is,the impact of rainfall on the embankment stability more sensitive.The lower the compaction degree of the predisintegration CM embankment near the slope is,the smaller the initial safety factor and the decrease of the safety factor of the embankment under the condition of rainfall.