甘肃北山芨芨采石场岩体节理特征研究

STUDY ON ROCKMASS JOINT CHARACTERISTICS OF JIJI QUARRY IN BEISHAN,GANSU PROVINCE

芨芨采石场是我国高放废物处置库甘肃北山预选区有利候选地段之一。采用综合节理测量法在芨芨采石场进行详细的节理调查,共获得13012条节理数据。根据芨芨采石场内的断层将该区域初步划分为3个岩体结构均质区和2个断层影响区。基于圆形窗口法原理编制计算程序,分析断层两侧节理的平均迹长和迹线中点面密度的变化,确定断层对节理分布的影响范围,准确划分岩体结构均质区的大小,并得出各均质区节理的平均迹长和迹线中点面密度;采用节理玫瑰花图和节理极点图法,得出各均质区节理的优势组,对各优势组的产状进行统计分析。芨芨采石场的岩体节理以陡倾角的剪节理为主,节理倾向和倾角符合正态分布;统计分析各优势组的节理间距,得出各优势组节理间距符合负指数分布。按照ISRM提出的《岩体不连续面定量描述的建议方法》(1978),采石场各结构均质区的节理间距都属于宽间距,表明岩体完整性较好。本次研究得到芨芨采石场岩体节理基本特征的定量化参数,为岩体力学和渗流特性的深入研究提供必要的数据。

Jiji quarry is one of the candidates in Beishan area,Gansu province—the preselected area for Chinese high-level radioactive waste repository. Data of 13 012 joints of granite are mapped by comprehensive joint survey method in Jiji quarry. According to the two faults,Jiji quarry is roughly divided into three regions where the structure of rockmass is homogenous and two regions which are influenced by the two faults. Based on the theory of the circular sampling window,the computing program is developed and is used to analyze the diversity of the mean joint trace length and joint trace midpoint density in the both sides of the faults. The boundaries of the rockmass structure homogenous region are determined according to the influential range of the faults;and the mean trace length and trace midpoint density of each rockmass structure homogenous region is calculated. The optimal joint sets of each rockmass structure homogenous region are obtained by rose diagram method and equal-area upper hemisphere projection method. The probability distributions of joint dip and dip angle can be effectively fitted by normal function;and the joint dip angles are mostly steep. The joint spacing of each set of joint is calculated and can be effectively fitted by negative exponential function. According to' suggested methods for quantitative description of discontinuities in rock mass'(ISRM,1978),the joint spacing of each rockmass structure homogenous region is wide. In this study,attention is focused on the rockmass joint characteristics,such as orientation,trace length,trace midpoint density and spacing. The quantitative parameters which can be used to describe the rockmass joint characteristics are obtained. They are essential for further research of the mechanical and seepage characteristics of rockmass.