基于3D打印技术复制砂浆节理的剪切试验及峰值抗剪强度模型

为进一步研究节理三维形貌特征与节理峰值抗剪强度的关系,首先采用巴西劈裂试验获取了自然劈裂岩石表面,通过三维扫描技术获取了节理面形态的高精度点云,通过逆向建模得到了自然岩石表面的立体模型,结合3D打印技术制作出了与自然岩石表面一致的PLA模具,以3D打印获得的底模通过水泥砂浆浇筑了含有自然结构面形貌的相似节理面试样。PLA模具与复制材料差异较大,复制材料在凝结过程中不易与PLA模具黏结,进而使脱模过程较为方便,不会破坏节理面。同时PLA模具可重复进行相似材料复制工作,具有可重复使用的优点。然后进行了具有5组形貌面的20个水泥砂浆节理面在4种不同法向荷载情况下的结构面剪切试验,得到了结构面剪切位移-荷载曲线。研究了结构面峰值抗剪强度、峰值位移、剪切刚度影响因素。节理经过剪切后形貌面出现不同程度的磨损,其磨损范围与等效高差分布范围基本一致,并且在等效高差为剪断破坏模式且成片的区域磨损较为严重。在新粗糙度指标基础上提出了新的峰值抗剪强度模型,经试验对比显示出新模型的有效性。在新模型基础上提出了一个简化模型。对比发现新模型简化后其计算精度较新模型有所降低但由于所需参数减小计算较为方便,新模型简化...

A model for estimating the peak shear strength of rock joints based on 3D quantified surface description

In order to further study the relationship between the characteristics of three-dimensional morphology and the peak shear strength of rock joints,the Brazilian splitting test was used to obtain the natural splitting joint surface,and the high-precision point cloud of the joint surface was obtained by 3 D scanning technology.The 3 D model of the natural joint surface was obtained by reverse modeling.Combining with the 3 D printing technology,the PLA base mould,which is consistent with the natural joint surface,was made.The base mould obtained by 3 D printing was poured with the natural joint surface through cement mortar.PLA mold and replica material are quite different,the replica material is not easy to bond with PLA mold during solidification process,which makes the demoulding process more convenient and does not destroy the joint surface.The direct shear tests were carried out on 20 groups of cement mortar joints to obtain the peak shear strength.After shearing,the joint surfaces show some different degrees of wear,and the wear distributions are approximately consistent with the equivalent height difference distribution.Moreover,the wear is obvious in the location where the equivalent height difference distribution shows shear failure mode.Then,a new peak shear strength model for rock joints was proposed using the new roughness parameter which can reflect that the different geometric parameters of the asperities have different contributions to the shear strength.It is shown that the predicted peak shear strength is well consistent with the experimental data.A simplified model was proposed based on the new model.The calculation precision of the simplified model is lower than that of the new model,but the calculation process is more convenient.