| Diatomite soil has the characteristics of high porosity,strong compressibility,strong structure,high sensitivity and so on.It is very prone to be damaged when under dry-wet circulation or external disturbances,resulting in a sharp decline in its mechanical properties.For the subgrade of ballastless track diatomite area,especially in the rainy area,if the rain seeps into the foundation,it will cause the diatomite soil to soften and then the foundation will cave in under the dead weight of upper structures and cyclic train-induced dynamic load.The settlement will lead to track irregularity,which may seriously affect the safe operation of the high-speed railway.Therefore,in order to prevent diatomite soil foundation from the influence of rainwater,the author conducted a comprehensive study on waterproof and drainage cutting subgrade for ballastless track in diatomite area.Here are the main research works:1.The waterproof and drainage technology for cutting subgrade has been studied completely.Introduce the structure of the waterproof and drainage cutting subgrade,which is a form of that two layers of coarse sand and a layer of capillary waterproof and drain board between them.And the construction materials are introduced,including capillary waterproof and drain board,AB class filler and graded broken stone.The construction technology,precautions and test and acceptance of the waterproof and drainage subgrade are also described in detail.2.According to the subject requirements and research content,the typical sections of waterproof and drainage subgrade and traditional subgrade were selected.Design the water immersion test and in-situ dynamic test and this paper introduces the experimental contents,equipment,sensors,experimental loading parameters and conditions,data collection and so on in detail.3.Water immersion test and in-situ dynamic test were carried out on the waterproof and drainage subgrade and the traditional subgrade.After the excitation of 2000000 times under different service conditions,the long-term performance,the attenuation along depth and crosssection direction of the dynamic stress,acceleration and velocity of subgrade are obtained.Besides that,the changes of soil moisture of different positions in subgrade before and after water immersion test are also available.Through analysis of the test results,it can be concluded that the structure layer of capillary waterproof and drainage plate has good waterproof and drainage effect and durability.4.Using the ABAQUS software,the three-dimensional finite element dynamic analysis models of the two kinds of subgrade were established,and the theoretical values of the dynamic stress and velocity of the subgrade along the depth and cross-section directions were obtained.Compared with the actual measured values,it can be known that the theoretical value is bigger than the test data,but the attenuation of the two is the same.5.The structure of the waterproof and drainage subgrade is optimized.The 40 cm graded broken stone layer is optimized to 37 cm graded broken stone + 3cm dense polyurethane graded broken stone layer with 8% content,which improves the waterproof and drainage performance of the surface layer of subgrade.By studying the dynamic characteristics and the waterproof and drainage performance,it is proved that the surface layer of subgrade after optimization has good stability and waterproof and drainage function. |
