CT Scan on Frozen Roadbed Soil under Dynamic Triaxial Test Condition ofBeilu River Section, Qinghai-Tibet Railway of China

摘要

As an effective scanning method with no damage, the CT scanning techniqueis used more widely in studying the dynamic deformation of frozen soil. Aiming atstability and dynamic deformation of frozen soil, the structural change before andafter a dynamic tri-axial test, failure type and their main affecting factors of frozensoil taken from roadbed of Qinghai-Tibet Railway are discussed from microstructureaccording to CT scanning results. It indicates that water content, temperature andconfining pressure are the main affecting factors. Change of density, strength andmodulus during dynamical deformation decreases with an increase of water contentand confining pressure, similarly the changes of the microstructure and structure.When temperature decreases, density, strength and modulus decrease rapidly, but themicrostructure and structural changes decreases. When axial dynamic strengthdecreases, degradation of density, strength, modulus changes from large to small atthe beginning and then from small to large, but structure change and demagnificationare the reverse of that. The dynamic failure type of the frozen soil depends on thecomposite in condition of higher water content and lower temperature, but belongs toloose expand and border cracking when water content is lower, belongs to equallyexpand type when confining pressure or temperature is higher, belongs to compositeand uniform expand type when confining pressure is lower and water content ishigher, and belongs to loose failure type when confining pressure is higher and watercontent is lower. To frozen soil, these CT scanning results and recognition not onlybenefit the study pf stability and dynamic deformation, but also provide importantdata for further dynamic characteristics studies and establishing dynamicdeformation models.