裂隙岩体岩石质量指标(RQD)的空间变化特征

Spatial Variation of Rock Quality Designation(RQD)in Fractured Rock Masses

岩石质量指标(RQD)是评价岩体破碎程度的一个重要参数,但在RQD的应用过程中往往忽略测线长度和测线方向的影响,给岩体质量的评价造成一定的误差。笔者通过从野外岩石露头这个二维平面上得到的RQD或节理参数,推导得到在三维空间中任意方向测线的RQD,进而研究RQD随测线方向的变化规律。结果表明,RQD不但在平面上具有各向异性,在空间也具有各向异性。笔者提出了假定测线起于节理的N-ARQD计算模型,使理论论证更加严密。此外,利用蒙特卡罗模拟产生随机值代表节理间距,随机值服从负指数分布的参数不同代表节理发育的密集程度不同,通过T-T、N-A、A-A和A-A-S 4种RQD计算模型来研究RQD均值及标准差随测线长度的变化规律,可以得出:测线越长,所得RQD值越精确;测线较短时,A-A-S模型所得的RQD值与其他3种模型相比更精确;布置较长的测线在节理较发育的地方可获得更可信的RQD值。

Rock quality designation （RQD）is the key parameter to evaluate the degree of fracturing of rock masses.There is error in rock mass evaluation when such factors as the scanline length and the scanline orientation are ignored.RQD or joint parameters is obtained on the field two-dimensional rock outcrop,RQD of any scanline orientation in three-dimensional space is derived,and the variation of RQD with the scanline orientation is studied.It shows that the RQD is anisotropy both in the space or and plane.The authors put forward the NA RQD calculate model that makes theoretical arguments more closely and the model assumed that the scanline from joints.Moreover,the Monte-carlo simulation is used to generate random values. Random values obeyed the negative exponential distribution with different parameters and were taken as the fracture spacings under varies of fractures development intensive degree.Then,the variation of mean and standard deviation of RQD values with the scanline length was studied by using four calculate models,i.e.TT model,N A model,AA model and AAS model.By comparison,some results are concluded as the follows：1the longer the scanline, the more accurate the RQD;2 the AAS model can obtain the more accurate RQD when the scanline was short;and 3 a much longer scanline was necessary for the more credible RQD in more fractured rock mass.