Study On Weathering Deformation After Unloading Of Red Mudstone

The constant up-deformation of excavated mudstone roadbed has become a difficult problem affecting the normal operation of high-speed railway.The systematic tests and theoretical research should be put forward to study the long-term deformation and influencing factors of mudstone.Study the deformation of mudstone under the effect of water and temperature and different unloading grades to reveal the deformation law of mudstone.Therefore,the paper explores the long-term deformation characteristics of mudstone under the change of water and temperature environment factors,and under different unloading grades,and reveals that the expansion deformation and shrinkage deformation are caused by weathering and microstructure change during soaking and dehydrating.The study results which are of theoretical and practical significance can provide some references for similar projects.The concrete research work and achievement of this paper are as follows.(1)According to the weathering and deformation characteristics of mudstone in natural environment,the experiment of drying-wetting cyclics weathering deformation of red-bed mudstone was carried out with lateral restraint based on the project.The results show that: the mudstone exhibits a charateristics of expansion deformation when soaking in the water,and shrinkage deformation during dehydrating.The strain in every cycle increases first and then becomes stable gradually over time;There is a positive correlation between the maximum strain of each sample and the initial moisture content of the sample along with the cycles continued.(2)In the view of the influence of load on weathering deformation of mudstone,the experiment was conducted to study the deformation under lateral restraint,drying-wetting cycles and axial stress(the similar stress at work site).The results show that: the results show that the deformation process of mudstone is similar to that of non-overlying stress,but the deformation value is different.The maximum strain on each cycle increases along with the increase of axial stress and there is occultate correlation with initial moisture content.In a drying-wetting cycle,the strain of expansion and shrinkage both decrease with the increase of axial stress.It is indicated that the existence of axial stress can obviously restrain the deformation of mudstone under the above conditions.(3)Based on the experimental data,the strain-time curves(within a cycle of dry-wet cycle)of mudstone samples with and without axial stress under soaking expansion and dehydrating shrinkage are analyzed.The results show that: the strain-time curve of expansion is in good agreement with the Logistics function,and the parameters can reflect the characteristics of variation of mudstone samples during the process of soaking deformation.The experimental data of shrinkage strain and maximum expansion strain of samples under each cycle are statistically analyzed by regression,and the empirical expressions are established,which can be used to predict the expansion strain deformation trend of muddy rocks.(4)A screening test for weathered fragments of mudstone samples was carried out.The results show that: the development degree of micorfissure determines the deformation value of mudstone samples during the whole drying-wetting cycles,and the more microfissure develop,the greater the final deformation of mudstone is.There is a positive correlation between the maximum strain value of the sample and the unonuniform coefficient of the weathered fragments.