中文摘要：

利用不同晶粒大理岩块加工成完整和含孔道的圆柱试样，在伺服实验机上分别进行单轴和常规三轴循环加载试验，其中三轴循环加载包括维持围压恒定和卸载围压两种情况．结果表明，循环加载确实可使试样的强度增加，强度大致提高5％-10％．岩石的材料强度和承载能力是两个不同的概念．大理岩晶粒之间多为裂隙，轴向压缩加载时晶粒局部接触应力远高于名义应力，在岩样未达到峰值应力之前，接触处已经产生很大的变形乃至出现局部破坏，形成的碎屑在卸载时可以脱落充填到附近的空隙，提高岩样承载能力．这种强化特征是与摩擦相关的承载能力，并非材料强度；与多次循环加载造成材料强度逐步劣化不同．从卸载点附近卸载与再加载应力应变曲线的关系，可以确认卸载是否引起岩石承载能力的增加．

英文摘要：

Marble specimens with various crystal sizes are uniaxially and pseudo-triaxially compressed in servo-controlled testing machine. Specimens are 50 mm in diameter and 100 mm in length, some of them have inner hollow of 10 mm in diameter. Experimental results show that specimens are strengthened 5% to 10% under cyclic loading. The material strength and loading capacity of rock are two different concepts. Marbles have many fissures between crystals, so contacted the stresses in crystals are much higher than nominal stresses, which will induce destroy and produce rock chips before the axial stress reaches its peak. These chips may fill the free walls of crystals when the specimen is unloaded. That results in the frictional healing of fissures. Obviously, the mechanism is different to fatigue failure under cyclic loading. The strengthen phenomena can be verified from the connection area of unloading and reloading stress-strain curves.