The shear behavior of the pipe-soil interface determines the frictional resistance of pipe jacking. In the interfacial direct shear tests of well-graded dense sand against steel pipe under both unlubricated and lubricated scenarios, the shear stress initially exhibits hardening followed by softening. The shear band forms in the hardening stage, and significant morphology of the shear band varies in the softening stage. Eventually, the shear band exhibits a bell-shaped distribution in the pattern of horizontal displacement influenced by boundary conditions and fabric anisotropy. Coarse particles exhibit greater displacement and more intense softening due to larger initial void ratios and rotational radius, while specimens with more fine particles possess smaller maximum vertical displacement away from the interface and larger critical interface friction angle. Increased normal stress restricts particle displacement, resulting in larger shear displacement at peak state, more severe particle breakage, reduced shear band thickness, and increased peak interface friction angle. The shear stress reaches the critical stage earlier with bentonite slurry (ω = 6 %) due to reduced dilatancy and particle breakage. When the slurry concentration exceeds 14 %, overall sliding of particle displacement occurs instead of the layered distribution with increased vertical particle movement and noticeable stress softening. Continuous accumulation of irreversible dilation might induce forward movement of overlying soil. Moreover, excessive slurry concentration increases hardening and interfacial friction coefficient.

中文翻译：

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基于数字图像相关 （DIC） 技术顶管中砂钢界面剪切行为的宏观/细观演变


管道-土壤界面的剪切行为决定了顶管的摩擦阻力。在未润滑和润滑情况下，级配良好的致密砂对钢管的界面直接剪切试验中，剪切应力最初表现为硬化，然后软化。剪切带在硬化阶段形成，剪切带的显著形态在软化阶段发生变化。最终，剪切带在受边界条件和织物各向异性影响的水平位移模式中表现出钟形分布。由于较大的初始空隙率和旋转半径，粗颗粒表现出更大的位移和更强烈的软化，而具有更多细颗粒的样品具有较小的远离界面的最大垂直位移和较大的临界界面摩擦角。增加的法向应力限制了颗粒位移，导致峰值状态下的剪切位移更大，颗粒破碎更严重，剪切带厚度减小，峰界面摩擦角增加。膨润土浆料 （ω = 6 %） 的剪切应力由于膨胀性和颗粒破碎性降低而提前达到临界阶段。当浆料浓度超过 14 % 时，颗粒位移发生整体滑动，而不是分层分布，颗粒垂直运动增加，应力明显软化。不可逆扩张的持续积累可能会诱导上覆土壤向前移动。此外，过高的浆料浓度会增加硬化和界面摩擦系数。