泥浆护壁工艺在钻孔灌注桩施工中应用广泛。受泥浆自身材料特性与其他施工条件的影响，孔壁上残积的泥皮会从本质上会改变桩-土界面的受力性状。为了深入探究含泥皮桩基桩-土界面的剪切力学特性，本文以黄土地区的钻孔灌注桩施工为工程背景，以黄土-泥皮-混凝土多元介质界面为研究对象，采用单因子控制变量法，在界面试样制备完成后开展室内直剪试验，深入分析不同参数对界面剪切特性的影响，并推导含泥皮桩基承载力的计算公式。本文研究内容主要包括以下几个方面：

（1）通过设定四种土体含水率与四种土体干密度水平，开展了不同土体参数下黄土-泥皮-混凝土界面剪切试验。在不同法向应力状态下，不同含水率及干密度水平对应的界面剪应力-剪切位移关系曲线特性明显不同。随着含水率及干密度的不断增大，对应界面抗剪强度分别随之减小和增大，两种条件下对应的粘聚力的变化幅度分别为86.91%与107.33%，均显著大于内摩擦角的变化幅度。

（2）通过设定四种混凝土粗糙度水平，以混凝土表面的平均凹凸程度R来量化界面粗糙度，开展了不同界面粗糙度下黄土-泥皮-混凝土界面剪切试验。在不同粗糙度水平与法向应力状态下，界面剪应力-剪切位移关系曲线均呈应变软化型，且随着法向应力的增大，曲线软化特征及界面抗剪强度的提升更为显著。

（3）通过设定四种泥皮厚度与四种水泥掺量水平，开展了不同泥皮参数下黄土-泥皮-混凝土界面剪切试验。当无泥皮界面转化为含泥皮界面时，剪应力-剪切位移曲线由硬化型转化为软化型。而泥皮中水泥掺量由低至高的过程中，剪应力-剪切位移曲线由软化型转化为硬化型。界面抗剪强度随着泥皮厚度及水泥掺量的增大，分别呈减小和增大趋势。当泥皮厚度达到一定值时，含泥皮界面趋于泥皮-混凝土界面，界面抗剪强度主要取决于泥皮自身强度。而随着水泥掺量的提升，含泥皮界面逐渐向无泥皮界面过渡。

（4）根据不同泥皮参数与含泥皮界面抗剪强度指标建立的相关联系，结合现行规范，对泥皮效应影响下桩基承载力的计算公式进行修正。同时利用FLAC3D有限差分软件建立三维数值模型，分别对不同工况下的桩基承载性状进行模拟分析，将公式计算结果与模拟计算结果进行对比，观察发现两者对应曲线的趋势大致相同且误差分别为6.65%与8.96%，处于合理范围内，验证了利用修正公式计算解决工程实际问题的合理性。

The mud wall protection technology is widely used in the construction of bored piles. Due to the material characteristics of the mud itself and other construction conditions, the residual mud skin on the hole wall will fundamentally change the stress characteristics of the pile soil interface. In order to deeply explore the shear mechanical characteristics of the interface between the pile and soil of the mud skin pile foundation, this paper takes the construction of drilled cast-in-place piles in the loess area as the engineering background, takes the loess mud skin concrete multi medium interface as the research object, adopts the single factor control variable method, and conducts indoor direct shear tests after the preparation of interface samples. The influence of different parameters on the shear characteristics of the interface is analyzed in depth, and the calculation formula for the bearing capacity of the mud skin pile foundation is derived. The research content of this article mainly includes the following aspects:

(1) By setting four soil moisture contents and four soil dry density levels, shear tests were conducted on the interface of loess clay concrete under different soil parameters. The characteristics of the interface shear stress shear displacement relationship curve corresponding to different moisture content and dry density levels are significantly different under different normal stress states. With the continuous increase of moisture content and dry density, the corresponding interface shear strength decreases and increases, respectively. The change amplitude of the corresponding cohesive force under the two conditions is 86.91% and 107.33%, both of which are significantly greater than the change amplitude of the internal friction angle.

(2) By setting four levels of concrete roughness and quantifying the interface roughness based on the average roughness R of the concrete surface, shear tests were conducted on the loess clay concrete interface under different interface roughness levels. At different roughness levels and normal stress states, the interface shear stress shear displacement relationship curve shows a strain softening type, and with the increase of normal stress, the softening characteristics of the curve and the improvement of interface shear strength are more significant.

(3) Shear tests were conducted on the interface between loess clay and concrete under different clay parameters by setting four different thicknesses of clay and four levels of cement content. When the interface without mud skin is transformed into the interface with mud skin, the shear stress shear displacement curve changes from hardening type to softening type. During the process of increasing the cement content in the mud skin from low to high, the shear stress shear displacement curve changes from a softening type to a hardening type. The interface shear strength shows a decreasing and increasing trend with the increase of mud skin thickness and cement content, respectively. When the thickness of the mud skin reaches a certain value, the interface containing the mud skin tends towards the mud skin concrete interface, and the shear strength of the interface mainly depends on the strength of the mud skin itself. As the cement content increases, the interface with mud skin gradually transitions to the interface without mud skin.

(4) Based on the correlation established between different mud skin parameters and the shear strength index of the interface containing mud skin, combined with current regulations, the calculation formula for the bearing capacity of pile foundation under the influence of mud skin effect is revised. At the same time, a three-dimensional numerical model was established using FLAC3D finite difference software to simulate and analyze the bearing behavior of pile foundations under different working conditions. The formula calculation results were compared with the simulation calculation results, and it was observed that the corresponding curve trends of the two were roughly the same, with errors of 6.65% and 8.96%, which were within a reasonable range. This verified the rationality of using the modified formula calculation to solve practical engineering problems.

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