桩土界面直剪试验装置设计与模拟应用

Design and experimental application of a direct shear test apparatus for the pile-soil interface

摘要:

为研究桩土界面力学特性，针对目前直剪试验较少考虑桩体弧形表面和实际粗糙度的问题，本文设计了一种可模拟实际工程桩弧形表面形态及粗糙度特征的直剪试验装置。该装置采用双剪切盒嵌套结构，通过上剪切盒螺栓加载系统与下剪切盒液压推进装置的协同作用，实现法向应力与切向位移的独立控制。试验基于现场实测数据，运用空间模型扫描技术和3D打印技术制作弧形表面混凝土桩模型，针对粉质黏土开展直剪试验，系统分析含水率、弧形界面粗糙度及法向应力对桩土界面力学特性的影响。试验结果表明，土体界面承载力随含水率增加呈先增后减的趋势，随界面粗糙度增大而显著提升，且与法向应力呈正相关，与实际情况相符，验证了装置设计的适用性与科学性，具有较强的工程应用价值。

Abstract:

To investigate the mechanical properties of the pile-soil interface， this study addresses the limitations of conventional direct shear tests in inadequately accounting for the curved surface morphology and actual roughness of pile bodies by designing a novel direct shear test apparatus capable of simulating the curved surface morphology and roughness characteristics of engineering piles. The apparatus features a nested dual-shear box configuration， wherein independent control of normal stress and tangential displacement is achieved through the synergistic operation of a bolt loading system in the upper shear box and a hydraulic actuation unit in the lower shear box. Using field-measured data， curved-surface concrete pile models were fabricated using spatial model scanning technology and 3D printing techniques， and direct shear tests were conducted on silty clay to systematically analyze the effects of moisture content， interface roughness of the curved surface， and normal stress on the mechanical properties of the pile-soil interface. Experimental results demonstrate that the interfacial bearing capacity exhibits a biphasic trend （initially increasing and subsequently decreasing） with rising moisture content， significantly increases with interface roughness， and shows a positive correlation with normal stress， all of which align with practical engineering conditions. These findings validate the applicability and scientific rigor of the apparatus design， demonstrating its practical engineering significance.