Sduty On The Settlement Characteristics Of Argillaceous Soft Rock Embankment On Expressway

Muddy soft rock is widely distributed in the southwest and northwest of China.In order to solve the problem of padding shortage,a large number of expressway projects use argillaceous soft rock waste to fill roadbed,which not only could reduce the cost of construction,but also reduce the occupation of cultivated land,and have achieved good environmental and economic benefits.However,the bad engineering characteristics of low strength,high weathering degree and softening disintegration under the action of water,resulting the roadbed settlement,the road surface craze and other diseases in the road operation process,which increases the maintenance cost,affects the driving comfort.It is important to study the stability of argillaceous soft rock embankment under different environments for practical engineering design and construction.Based on the He-Chang expressway project,four kinds of argillaceous soft rock embankment structures are designed.The engineering characteristics of filling materials and settlement characteristics of various types of embankments are systematically studied,by the means of field investigation,indoor test,centrifuge model test,numerical analysis,theoretical calculation and field test.The main research contents and results are as follows:1.The microstructure,mineral composition and diffraction patterns of rocks before and after disintegration were studied by electron microscopy and X ray diffraction,and the mechanism of disintegration of muddy soft rocks in water was revealed.2.A large number of laboratory tests have been carried out to study the anti disintegration of soft rock and the strength of point load,as well as the engineering properties such as compaction effect,CBR value,shear strength and compressibility of the filler,the research shows that the argillaceous soft rock has the characteristics of strong disintegration(I_d2?30)and low strength,but all the indexes of the filler can meet the requirements of the“highway subgrade design specification”,and provide a reliable basis for evaluating the road performance.3.Through the centrifuge model test and numerical analysis,the settlement characteristics of four structural forms?ordinary embankment,sandwich type,hemming type,3%cement improved?argillaceous soft rock embankment are studied.,the results show that:Firstly,under normal working conditions,the settlement of argillaceous soft rock embankment mainly occurs in the construction filling stage,accounting for 62.96%to 65.83%of the total.From the settlement and deformation trend,the clay sandwich layer and a small amount of cement effectively improve the overall strength of the embankment,and the settlement deformation is small.Secondly,under the condition of continuous rainfall,the settlement deformation of embankments with four structural forms is quite different.The settlement of ordinary embankment and sandwich embankment is"M"along the section,and the shoulders and slopes on both sides collapse.The influence of rainfall is relatively small on the hemming type and 3%cement improvement embankment.Thirdly,under normal working conditions,the lateral deformation of the embankment is in a"bow"shape,and the maximum deformation occurs at 2.0m from the base,with little deformation.Under continuous rainfall,the lateral deformation trend decreases from base to top,and the lateral deformation of embankment increases,especially the ordinary argillaceous soft rock embankment.4.Considering the unidirectional and three directional deformation of embankment,the settlement of argillaceous soft rock under different working conditions were calculated.The linear fitting of theoretical calculation and other research conclusions is realized by using the cftool toolbox of MATLAB software.Based on the creep effect of filler,the time correction coefficient?for vertical settlement.5.Through field test,the filling parameters of argillaceous soft rock embankment are determined.The construction time of the pavement structure layer and the reserved height of the embankment are determined according to the test results of the embankment settlement monitoring.