The freezing and thawing cycle results in spalling hazards in loess slope in Luochuan. For comparison , the samples of loess suffering from spalling hazards in Luochuan and those not spalling have been collected respectively. In order to simulate the freezing and thawing process of the natural loess slopes, the test on the freezing and thawing cycle is carried out in the open conditions without any water being replenished, which is to observe the change of the properties of soil samples on the surface as well as its height, dry density, water content, cohesion and internal frictional angle under the function of freezing and thawing cycle. The test results indicate that in the first few cycles, the samples collected from Luochuan have slight increase in volume and water content The soil structure is destroyed by the icy freezing expansive force in the process, which cannot berecovered in the thawing process. The soil strength is weakened by repeated freezing and thawing processes, After about ten cycles of freezing and thawing, the phy si co-mechanical condition of soil tends to be stable. While in the thawing process, the interface of water and ice has the softening function of water and the facilitating effect. If there is very good exposed surface, the spalling hazards in loess slopes may easily occur along this interface between water and ice; the negative pore water pressure may occur at the frozen edge in the process of freezing of soil samples. The soil density increases, while the volume decreases, and the soil strength is enhanced; in the process of thawing, the effective stress reduces; the total stress remains unchanged; the thawing volume is larger than the frost heaving amount The cohesion of soil is slightly enhanced; therefore, it is not likely to have spalling hazards.%冻融循环作用导致洛川黄土边坡剥落病害的发生.作为对比,在洛川剥落边坡及铜川未剥落边坡分别采样,模拟自然坡面冻融过程,在开放不补水条件下,开展冻融循环试验,测定在冻融循环作用下土样表面的变化特征及土样高度、干密度、含水率、黏聚力及内摩擦角的变化情况.试验结果表明:洛川土样在初始几次冻融过程中,土样体积稍有增大,含水率变化较大,冻结过程中冰晶冻胀力破坏土体结构,融化时结构不可恢复,反复冻融导致土体强度弱化.冻融循环10次左右后,土体物理力学状态趋于稳定.融化时,在水的软化作用和冰的促化效应下,沿着水冰交界面易产生剥落病害；铜川土样在冻结过程中,在冻结缘处产生负孔隙水压力,土体密度增大,体积减小,强度增大；融化时,有效应力减小,总应力不变,融沉量大于冻胀量,土体黏聚力略有增强,不易产生剥落.
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