基于数字钻探的岩石c-φ参数测试方法

岩石黏聚力c和内摩擦角φ(以下简称c-φ参数)的准确测试是进行地下工程支护设计优化及信息化施工的基础。传统的岩石室内试验方法测试步骤繁琐,周期长、成本高,无法进行原位测定。数字钻探技术为现场准确测定岩石力学参数提供了新的途径,实现该技术的关键在于建立随钻参数与岩石c-φ参数间的定量关系。基于此,本文根据岩石切削破碎特征,建立了一种不预设破坏面的岩石切削力学模型,弥补了现有岩石切削力学模型将破坏面假设为平面,从而与岩石受切削时实际的破坏面特征存在差异的不足。基于滑移线理论推导了岩石极限切削力,得到了随钻参数DP(Drilling Parameters)与岩石c-φ参数关系式(DP-cφ关系式)。将利用自主研发的岩体数字钻探测试系统开展室内试验所得到的随钻参数与理论计算得到的结果进行对比分析,两者平均差异率为8.44%,验证了所建立的岩石切削力学模型和DP-cφ关系式的合理性和正确性。在此基础上,提出了岩石c-φ参数数字钻探测定方法,并通过室内试验进行了该方法与传统三轴试验方法测定结果的对比分析,结果表明:两种方法得到的岩石黏聚力和内摩擦角平均差异率均小于10%,证明了本文所提出的数字钻探测定方法的有效性和可行性。该方法实施方便、快捷,可实现现场工程岩体c-φ参数的原位测定。

A testing method for rock c-φ parameter based on digital drilling test technology

The accurate measurement of rock cohesion c and internal friction angle φ (hereinafter referred to as the c-φ parameter) is the basis of optimizing the design of underground engineering support and information construction.The traditional indoor test method has the characteristics of cumbersome testing steps,long cycle and high cost,and cannot carry out in-situ measurement.Therefore,it is necessary to develop an accurate and fast on-site testing method for rock c-φ.Digital drilling testing technology provides a new way for accurate and fast prediction of rock c-φ in-situ,and the key is to establish the quantitative relationship between drilling parameters and rock c-φ.According to the fracture characteristics of rock cutting,a rock cutting mechanics model without prior assumption of failure surface is proposed.This model makes up for the deficiency of the existing rock cutting mechanics model that assumes the failure surface as a plane and thus differs from the actual characteristics of the failure surface in rock cutting.The ultimate cutting force is deduced on the basis of the slip-line theory.Based on this,the relationship between drilling parameters (DP) and c-φ parameter (hereinafter referred to as the DP-cφ relationship) is established.In this paper,the digital drilling test is carried out by using the self-developed digital drilling test system.Compared with the results of theoretical analysis and laboratory test,the average difference is 8.44%,which verifies the rationality and correctness of the rock cutting mechanics model and the DP-cφ relationship.Therefore,a digital drilling measurement method for the rock c-φ parameter is proposed.Compared with the results of this method and traditional triaxial method through laboratory tests,the average difference rate of cohesion and internal friction angle obtained by the two methods are less than 10%,which proves the feasibility and effectiveness of the digital drilling method proposed in this paper.The method is convenient and fast,and can realize in-situ measurement of the c-φ parameter of the rock mass in the field.