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

As an effective scanning method with no damage, the CT scanning technique is used more widely in studying the dynamic deformation of frozen soil. Aiming at stability and dynamic deformation of frozen soil, the structural change before and after a dynamic tri-axial test, failure type and their main affecting factors of frozen soil taken from roadbed of Qinghai-Tibet Railway are discussed from microstructure according to CT scanning results. It indicates that water content, temperature and confining pressure are the main affecting factors. Change of density, strength and modulus during dynamical deformation decreases with an increase of water content and confining pressure, similarly the changes of the microstructure and structure. When temperature decreases, density, strength and modulus decrease rapidly, but the microstructure and structural changes decreases. When axial dynamic strength decreases, degradation of density, strength, modulus changes from large to small at the beginning and then from small to large, but structure change and demagnification are the reverse of that. The dynamic failure type of the frozen soil depends on the composite in condition of higher water content and lower temperature, but belongs to loose expand and border cracking when water content is lower, belongs to equally expand type when confining pressure or temperature is higher, belongs to composite and uniform expand type when confining pressure is lower and water content is higher, and belongs to loose failure type when confining pressure is higher and water content is lower. To frozen soil, these CT scanning results and recognition not only benefit the study pf stability and dynamic deformation, but also provide important data for further dynamic characteristics studies and establishing dynamic deformation models.