冻融循环下橡胶-砂胶结材料力学特性试验

在季节性冻土区，冻融作用将改变桩周土体的强度，并诱发桩基发生病害，研制桩周土体置换材料，探明温度及冻融循环对其力学特性的影响机理，对于季节性冻土区桩基冻融与冻胀病害的防治非常必要。利用橡胶颗粒、砂和聚氨酯胶黏剂制作试样；开展不固结不排水三轴压缩试验，获得不同条件下橡胶-砂胶结材料试样的应力-应变曲线；并通过非线性拟合和回归分析，建立试样切线模量和切线泊松比与轴向、径向应变之间的拟合关系式；据此分析了橡胶-砂胶结材料试样在不同的冻融循环次数、温度及围压等条件下的力学特性。结果表明：橡胶-砂胶结材料试样的应力-应变曲线没有峰值点，为典型的应变硬化型材料；橡胶-砂胶结材料的切线模量介于2.0～9.0 MPa之间，温度对试样破坏强度和切线模量的影响较大，而冻融循环次数和低围压对试样破坏强度和切线模量的影响相对较小；橡胶-砂胶结材料试样的切线泊松比介于0.50～0.75之间，径向应变越大，切线泊松比也越大。相对而言，切线泊松比受冻融循环次数、温度及低围压的影响并不明显，可忽略不计。橡胶-砂胶结材料有望为季节性冻土区桩基冻融与冻胀病害防治提供支撑。

Experimental Study on Mechanical Properties of Rubber-sand Cementing Materials Under Freeze-thaw Cycles

In seasonally frozen soil areas, freezing and thawing change the strength of the soil around the pile and induce diseases of pile foundations. Therefore, it is necessary to develop a new material which can replace the soil around the pile and to determine the influence mechanism of temperature and freeze-thaw cycles on the mechanical properties. Rubber particles, sands, and polyurethane glues were proportioned to prepare triaxial testing samples. Unconsolidated and undrained static triaxial tests were performed to obtain the stress-strain curves of the samples under different test conditions. Subsequently, the fitting relationships between the tangent modulus, tangent Poisson's ratio, and axial and radial strains were established by nonlinear fitting and regression analysis. The effects of freeze-thaw cycles, test temperatures, and confining pressures on rubber-sand cementing materials were analyzed. The results show that the stress-strain curves of rubber-sand cementing material samples have no peak point, so the material is a typical strain hardening material. The tangent modulus of rubber-sand cementing materials is between 2.0 MPa and 9.0 MPa. The temperature has a significant influence on the failure strength and tangent modulus of the sample, while the number of freeze-thaw cycles and low confining pressures have relatively less influence. The tangent Poisson's ratio of rubber-sand cementing materials is approximately 0.50-0.75, and increases with an increase in radial strain. However, the tangent Poisson's ratio is not significantly affected by the number of freeze-thaw cycles, temperatures, and low confining pressures. Rubber-sand cementing materials are expected to provide support for freezing-thawing and for the prevention of frost heaving in pile foundations in seasonally frozen soil areas.