Study On Mechanical Properties And Embankment Deformation Characteristics Of Carbonaceous Mudstone Coarse-grained Soil Filler Under Dynamic Humidification

As an embankment filling material,carbonaceous mudstone contains a large amount of hydrophilic minerals in its particles,which will expand and soften when encountering water,causing subsequent disintegration and sharp deterioration of mechanical properties.During rainfall,rainwater will infiltrate into the subgrade through the voids on the road surface,and under the repeated loading of vehicles,the strength of the carbonaceous mudstone coarsegrained soil particles will decrease rapidly,resulting in a significant weakening of the embankment properties and reducing the service life of the embankment.In order to study the change law of mechanical properties of carbonaceous mudstone coarse-grained soil under the action of dynamic humidification,this paper firstly carried out a particle compression and crushing test on the carbonaceous mudstone coarse-grained soil under the action of dynamic humidification to explore the change law of its particle strength.Then,according to the changing trend of gradation of carbonaceous mudstone coarse-grained soil after dynamic humidification loading,a large-scale indoor static triaxial test was carried out,and the variation law of shear strength parameters of carbonaceous mudstone coarse-grained soil under different gradations was obtained.The dynamic response and deformation characteristics of the carbonaceous mudstone coarse-grained soil embankment under the action of dynamic humidification were simulated and analyzed using triaxial test data and numerical simulation software.The main conclusions of this study are as follows:(1)With the increase of water content,the particle crushing fractal dimension D and inherent crushing strength σc of carbonaceous mudstone coarse-grained soil gradually decreased.After the particles reach a saturated state,the crushing fractal dimension D and inherent crushing strength of the carbonaceous mudstone will gradually decrease with the increase of the duration of the dynamic load,while the crushing fractal dimension D and the inherent crushing strength of the mudstone under the static load change.smaller.(2)The values of particle crushing strength and characteristic stress σ0 of carbonaceous mudstone coarse-grained soil decrease gradually with the increase of water content.The characteristic stress value of granular soil will basically maintain a certain stable state,and will not change significantly with the increase of time.(3)When the loading time is the same,the characteristic stress σ0 of carbonaceous mudstone coarse-grained soil will decrease with the increase of particle size,and the size effect is obvious;the characteristic stress σ0 of mudstone particles in the same particle size group will decrease with the dynamic pressure loading time The increase gradually decreases;the characteristic stress σ0 of the carbonaceous mudstone coarse-grained soil of each particle size group shows a gradually exponential decreasing trend with the increase of the dynamic humidification loading time;The increase will make the coarser particles in the particle gradation of carbonaceous mudstone coarse-grained soil appear more brittle,and the content of coarse particles in the sample gradation gradually decreases,while the content of fine particles gradually increases.(4)Under different confining pressures,the stress-strain relationship curves of the triaxial samples of carbonaceous mudstone at all levels show obvious nonlinear relationship.Hardened type.The shear strength parameters of the samples,cohesion C and internal friction angle φ,have an approximate linear relationship with the fractal dimension.When the content of coarse particles in the gradation gradually decreases,the shear strength parameters of the samples,cohesion c and The internal friction angle φ will gradually increase.(5)On the same level,the monitoring point closest to the track of the wheel has the largest vertical stress peak;as the depth gradually increases from the top surface of the subgrade,the impact of the traffic load on the subgrade is smaller,and the vertical stress at the depth of 2m is smaller.The peak value is 13kPa,which is 59%lower than the 32kPa at the top surface of the roadbed.When the number of driving loads is small,the deformation of the carbonaceous mudstone coarse-grained soil embankment is mainly elastic strain,and the decreasing trend of the safety factor is not obvious.The slope safety factor gradually decreases.