Abstract Pile jacking is a kind of competitive method for pile installation due to its less noise and vibration pollution. In this paper, the pile jacking process has been numerically simulated by considering the friction fatigue, and the characteristics of sand-pile interface shear paths at different depths were thoroughly investigated. It is found that during the cyclic jacking process, the interface shear path at a specified depth tends to transform from one-way shear to two-way shear, especially for the shallow to middle depth. But for the deep soil layer, one-way cyclic shear is still the dominated loading mode. Focusing the effects of different paths on the sand-pile interface shear behaviours, a series of cyclic interface shear tests have been conducted, in which two types of sands and four typical shear paths were adopted. It has been revealed that during continuous jacking process, the sample volume response changes significantly with different interface shear paths. The previous shear path also plays a key role in the cyclic degradation of interface strength with CNS (constant normal stiffness) condition. If the sample contraction is small during jacking process, the cyclic degradation of interface strength is obvious. But, when the sample contraction during jacking process is significant, the interface strength degradation is largely suppressed. This is mainly because the abundant broken fine particles along the pile shaft will fill into the voids and make the sand sample near the interface much denser. It is shown that the changes of pile-soil interface characteristics will affect the pile responses.

中文翻译：

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循环顶进对砂桩界面剪切行为的影响

摘要 顶桩由于其噪声和振动污染较小，是一种较有竞争力的打桩方法。本文通过考虑摩擦疲劳对顶桩过程进行了数值模拟，深入研究了不同深度砂桩界面剪切路径的特征。研究发现，在循环顶进过程中，指定深度的界面剪切路径趋向于由单向剪切向双向剪切转变，尤其是浅层到中层深度。但对于深层土层，单向循环剪切仍是主导加载方式。针对不同路径对砂桩界面剪切行为的影响，进行了一系列循环界面剪切试验，试验中采用了两种类型的砂和四种典型的剪切路径。结果表明，在连续顶升过程中，样品体积响应随界面剪切路径的不同而显着变化。先前的剪切路径在具有 CNS（恒定法向刚度）条件下的界面强度循环退化中也起着关键作用。如果在顶升过程中样品收缩很小，界面强度的循环退化是明显的。但是，当样品在顶升过程中收缩显着时，界面强度退化在很大程度上得到抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。样品体积响应随界面剪切路径的不同而显着变化。先前的剪切路径在具有 CNS（恒定法向刚度）条件下的界面强度循环退化中也起着关键作用。如果在顶升过程中样品收缩很小，界面强度的循环退化是明显的。但是，当样品在顶升过程中收缩显着时，界面强度退化在很大程度上得到抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。样品体积响应随界面剪切路径的不同而显着变化。先前的剪切路径在具有 CNS（恒定法向刚度）条件下的界面强度循环退化中也起着关键作用。如果在顶升过程中样品收缩很小，界面强度的循环退化是明显的。但是，当样品在顶升过程中收缩显着时，界面强度退化在很大程度上得到抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。先前的剪切路径在具有 CNS（恒定法向刚度）条件下的界面强度循环退化中也起着关键作用。如果在顶升过程中样品收缩很小，界面强度的循环退化是明显的。但是，当样品在顶升过程中收缩显着时，界面强度退化在很大程度上得到抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。先前的剪切路径在具有 CNS（恒定法向刚度）条件下的界面强度循环退化中也起着关键作用。如果在顶升过程中样品收缩很小，界面强度的循环退化是明显的。但是，当样品在顶升过程中收缩显着时，界面强度退化在很大程度上得到抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。当顶升过程中样品收缩显着时，界面强度退化得到很大程度的抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。当顶升过程中样品收缩显着时，界面强度退化得到很大程度的抑制。这主要是因为沿桩身大量破碎的细颗粒会填满空隙，使界面附近的砂样更加致密。结果表明，桩土界面特性的变化会影响桩的响应。