通过4组不同密度的粗粒土大型三轴压缩试验，研究了密度和围压对力学性质的影响。成果表明:对于同一种粗粒土，密度和围压是影响力学性质的重要因素，它们共同决定了粗粒土的应力应变曲线形态。疏松的粗粒土一般表现为应变硬化型和体积压缩，随着围压的增大，应力应变曲线的硬化特征更加明显，体缩变形也增大。密实的粗粒土在低围压下应力应变曲线一般呈软化型，且常常表现出较大的体胀变形；高围压下，则表现出硬化特征和体缩特征。密度相同时，围压越高，粗粒土的抗剪强度也越高；围压一定时，粗粒土的残余强度相同。初始孔隙比小的粗粒土在相同的应力状态下体积变形也较小。密度是决定初始弹性模量的根本因素，而剪切变形过程中弹性模量则是密度和应力状态共同决定的。三轴压缩试验条件下，剪应力引起的体积变形一般是先剪缩后剪胀的，其大小由密度和应力状态决定。

Influences of density and confining pressure on mechanical properties for coarse-grained soils were researched by four groups large-scale triaxial compression tests. The results show as follows: Density and confining pressure are important factors affect mechanical properties for one coarse-grained soil, and they decide the stress-strain curve shape. Loose coarse-grained soils usually behave strain hardening and volume shrinking, the hardening characteristic of stress-strain curve becomes distinct and the volume shrinking strain increases with the increase of confining pressure. Dense soils commonly represent strain softening and bigger volume dilatancy strain under low confining pressure, but at high confining pressure coarse-grained soils usually show hardening and volume shrinking characteristics. When the density is same, the higher the confining pressure, the higher the shear strength. If the confining pressure is equal, the residuary shear strength is equal too. The deformation is small when the initial void ratio is low under the same stress status. Density is the essential factor to decide the initial elastic modulus, and the elastic modulus in shear process is the result of combined action of stress status and density. The volumetric strain induced by shear stress is shrinking at first, then dilating later under triaxial compression test conditions, of which the value is determined by density and stress state.