水泥改良土的拉伸强度特性及其计算方法

水泥改良土具有强度高、变形小、施工操作简单、质量控制容易和经济效益显著等优点，被广泛应用于路基填筑、基坑回填、边坡防护和地基换填。水泥土裂缝影响路基工程的正常运行，甚至可能危及铁路路基安全。因此，铁路路基设计需要对路基填土的抗拉强度有一定程度的了解，水泥改良土抗拉强度的确定具有重要意义。水泥改良土的抗裂性能是影响工程应用的重要因素，拉伸强度是衡量水泥土抗裂性能的关键指标。本文基于常规无侧限压缩仪自行设计了直接测量水泥改良土拉伸强度的单轴拉伸试验方法，系统地研究了水泥掺量（A）、龄期（t）、含水率（w）和干密度（ρ_d）对水泥改良土单轴拉伸强度（σ_t）的影响，水泥改良土的单轴拉伸强度随水泥掺量、龄期和干密度增加而增加，随含水率增加而减小，建立了水泥改良土的单轴拉伸强度与e_t/A（e_t是水泥改良土的孔隙比）之间的指数函数关系。结合水泥改良土的无侧限抗压强度和基质吸力的测试结果，建立了单轴拉伸强度与无侧限抗压强度和基质吸力之间的相关关系。

Tensile strength characteristics and calculation methods of the cement stabilized soil

Cement stabilized soil has the advantages of high strength, small deformation, simple construction operation, easy quality control and remarkable economic benefits. It is widely used in subgrade filling, foundation pit backfilling, slope protection and foundation replacement. Soil-cement cracks affect the normal operation of roadbed engineering and may even endanger the safety of railway roadbed. Therefore, the design of cracks and deformation structures of railway subgrade or foundation requires a certain degree of understanding of the tensile strength of the compact-filled soil, and it is of great significance to determine the tensile strength of the cement-improved soil. The crack resistance of the cement stabilized soil is an important factor affecting engineering application. Tensile strength is the key parameter to measure the crack resistance of the cement stabilized soil. In this paper, a direct test method to measure the tensile strength of the cement stabilized soil is designed in the conventional unconfined compression apparatus. The effects of cement content, curing age, water content and dry density on the tensile strength of the cement stabilized soil are systematically studied. The tensile strength of the cement stabilized soil increases with the increasing cement content, curing age and dry density, and decreases with the increasing moisture content. The exponential function relationship between the tensile strength and e_t/A (e_t is the void ratio of cement stabilized soil) is established. The correlation between the tensile strength and unconfined compressive strength and matrix suction is also statistically established.