Rock slope stability assessment through rock mass classification systems

Over the last several decades, rock mass classification systems have been proposed in order that cuttings at high risk for failure be identified, and preventive measures be effectively prioritized. The present paper attempts a review of the systems in question, illustrating the main differences and similarities among them, which are focused on the types of failures considered and the factors involved. The reliability of these systems is discussed as well. Relatively, these systems contain factors which raise queries about their suitability or the manner by which they are attributed into them. Moreover, although a rock cut failure event presupposes the action of a triggering factor (e.g., earthquake, precipitation), rock mass classification systems, by omitting it, do not classify cuttings according to their actual hazard (potentiality) for failure. Groundwater, when it is not erroneously ignored, is taken into account as instability factor with limited effect upon the systems (<15%) and not as a triggering factor for failure. Additionally, a number of suggestions regarding rock mass classification systems are given. Relatively, it is recommended rock cuttings to be classified according to their failure hazard taking into account both their condition and the influence of triggering factors upon stability. Moreover, each type of failure should be examined independently, as each one of them is governed by specific instability factors. Finally, some recommendations concerning amalgamation of factors, the possible ways that water may trigger a failure and the quantification of the most common triggering factors for failure (earthquake and precipitation) are provided.     

Application of rock mass classification systems to rock slope stability assessment: A case study

The stability of rock slopes is considered crucial to public safety in highways passing through rock cuts, as well as to personnel and equipment safety in open pit mines. Slope instability and failures occur due to many factors such as adverse slope geometries, geological discontinuities, weak or weathered slope materials as well as severe weather conditions. External loads like heavy precipitation and seismicity could play a significant role in slope failure. In this paper, several rock mass classification systems developed for rock slope stability assessment are evaluated against known rock slope conditions in a region of Saudi Arabia, where slopes located in rugged terrains with complex geometry serve as highway road cuts. Selected empirical methods have been applied to 22 rock cuts that are selected based on their failure mechanisms and slope materials. The stability conditions are identified, and the results of each rock slope classification system are compared. The paper also highlights the limitations of the empirical classification methods used in the study and proposes future research directions.     

A generic method for rock mass classification

Rock mass classification (RMC) is of critical importance in support design and applications to mining, tunneling and other underground excavations. Although a number of techniques are available, there exists an uncertainty in application to complex underground works. In the present work, a generic rock mass rating (GRMR) system is developed. The proposed GRMR system refers to as most commonly used techniques, and two rock load equations are suggested in terms of GRMR, which are based on the fact that whether all the rock parameters considered by the system have an influence or only few of them are influencing. The GRMR method has been validated with the data obtained from three underground coal mines in India. Then, a semi-empirical model is developed for the GRMR method using artificial neural network (ANN), and it is validated by a comparative analysis of ANN model results with that by analytical GRMR method.     

黄土隧道的围岩分级方法及应用

以绥延高速长岭山1号隧道工程为依托,根据地质调绘资料及土工试验数据,对该隧道进行了围岩分级,指出该方法准确可靠,为今后陕北地区黄土隧道的设计及施工提供了参考依据。     

Correlations between rock mass intactness index (Kv) and other rock mass classification indices (RMR89 system and GSI)

Bulletin of Engineering Geology and the Environment - Rock mass integrity is related to rock mass quality and strength. It can be characterized by a single index, or a combination of multiple...     

Revisiting rock classification to estimate rock mass properties

This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation,spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index(GSI) and relationships to estimate the Hoeke Brown failure criterion parameters, mb, s and a, are presented.     

An alternative rock mass classification system for rock slopes

A system for the quantification of the failure hazard of rock cuttings structured in the form of rating tables is proposed. Rock cuttings are classified according to their failure hazard taking into account both their drained condition and the influence that climatic conditions have on stability; the latter being the most common landslide-triggering factor. The system deals with seven types of failure including slides, topples and falls. Where possible and convenient, parameters are amalgamated using well-established expressions of safety factor increasing the objectivity of the system. In addition to triggering mechanisms, site-specific parameters related to the mean and critical precipitation height, as well as the potential for the development of adverse, water-related conditions are taken into account to arrive at a Hazard Index value.     

Principal conversion methods for rock mass classification systems used at home and abroad

This paper presents the pruposes and significance of rock mass classification systems. It further proposes the contrast and conversion among the principal rock mass classification systems and outlines its foundations, principles and methods. For the convenience of engineering application, the contrast and conversion tables and some practical examples are also demonstrated here.     

Development of an expert system for rock mass classification

This paper documents the development of an expert system for rock mass classification for use on microcomputers. The expert system called. EMC was. developed using an expert system shell FLOPS. FLOPS is a shell based on the Al language 0PS5 with many unique features. The system RMC utilizes most of these unique features. Among the features used are approximate reasoning with fuzzy sets, the blackboard architecture and the emulated parallel processing of fuzzy production rules. Details of the development of RMC including discussion of some relevant fuzzy set backgrounds are described in this paper.     

A methodology for evaluation and classification of rock mass quality on tunnel engineering

In this paper a new methodology for evaluation and classification of rock mass quality that can be applied to rock tunneling is presented. An evaluation model based on combing the analytic hierarchy process (AHP) and the fuzzy Delphi method (FDM) for assessing the rock mass rating is the main procedure. This research treats rock mass classification as a group decision problem, and applies the fuzzy logic theory as the criterion to calculate the weighting of factors. The main advantage of this procedure is that it can effectively change the weighting of each rating parameter with the variation of geological conditions. The proposed method was evaluated and applied to the actual cases that are the two tunnels along the Second Northern Highway around Taipei area in Taiwan, namely Mu-Zha and Hsin-Tien tunnels. It was found that the determined results were in a good agreement with the original data assessed by the RMR. Results of the analyses show that it can be provided a more quantitative measure of rock mass and hence minimize judgmental bias. The proposed method should be more feasible for future tunnel construction and for suggestions of tunnel support design in the geological area of Taiwan.     

Influence of data analysis when exploiting DFN model representation in the application of rock mass classification systems

Discrete fracture network (DFN) models have been proved to be effective tools for the characterisation of rock masses by using statistical distributions to generate realistic three-dimensional (3D) representations of a natural fracture network. The quality of DFN modelling relies on the quality of the field data and their interpretation. In this context, advancements in remote data acquisition have now made it possible to acquire high-quality data potentially not accessible by conventional scanline and window mapping. This paper presents a comparison between aggregate and disaggregate approaches to define fracture sets, and their role with respect to the definition of key input parameters required to generate DFN models. The focal point of the discussion is the characterisation of in situ block size distribution (IBSD) using DFN methods. An application of IBSD is the assessment of rock mass quality through rock mass classification systems such as geological strength index (GSI). As DFN models are becoming an almost integral part of many geotechnical and mining engineering problems, the authors present a method whereby realistic representation of 3D fracture networks and block size analysis are used to estimate GSI ratings, with emphasis on the limitations that exist in rock engineering design when assigning a unique GSI value to spatially variable rock masses.     

基于MCS-TOPSIS耦合模型的岩体质量分类研究

 岩体质量分类是各类岩土工程实践问题的基础,由于岩体指标参数的模糊性和随机性,故岩体质量分类表现出不确定性,而现有分类模型则忽略了这种参数不确定性对分类结果造成的影响。考虑到分类指标参数的不确定性,在岩体质量分类问题中引入概率描述的可靠度分析方法,提出一种蒙特卡洛模拟(Monte Carlo simulation,简称MCS)和逼近理想解排序法(technique for order preference by similarity to ideal solution,简称TOPSIS)耦合模型。该模型由两部分组成：通过博弈论赋权方法获取分类体系中指标的权重,并结合TOPSIS模型来建立可靠度分析中的极限状态方程;基于MCS方法由TOPSIS模型构建的极限状态方程进行随机的不确定性分析,并通过概率函数给出最终的分类结果。通过25组测试样本对基于博弈论组合赋权的TOPSIS模型进行测试,结果显示该模型的误判率为0,表明MCS-TOPSIS模型中确定性分析的合理性。最后通过Matlab语言编制计算程序,分别由确定性分析和不确定性分析的角度来探讨水布垭地下洞室厂房围岩质量分类。研究结果表明：采用MCS-TOPSIS模型进行岩体质量分类是可行的,该模型具有较高的准确度且易于实现,具有一定的工程应用价值。该研究为岩体质量分类提供了一种新思路。     

A new tunnel inflow classification (TIC) system through sedimentary rock masses

A new classification system with respect to the engineering geological characteristics of rock masses in different geological conditions were presented based on the authors’ experiences and observations. Rock mass composition (RMC), rock type (RT), clay-bearing content (CBC), unconfined compressive strength (UCS) and tunnel depth (TD) were found as the major factors affecting the tunnel inflow. In order to minimize judgmental bias and set up a basic database, data pertaining to these factors were compiled from 33 tunnels project with a total length of about 200 km thoroughly excavated in sedimentary rocks. The classification factors were rated using a combination of the analytic hierarchy process (AHP) and statistical methods. In order to cover all rock mass varieties and lessen the uncertainties, major factors were divided into categories of varying quality. Two statistical criteria were introduced to calculate the weighing of categories. The main advantage of this procedure is its capability of effectively predicting groundwater inflows in a vast variety of geological conditions especially from a single flow pathway such as a brittle fault zone to low permeable rock masses. The proposed classification was applied to the actual rock tunnels. It was revealed that the predicted values were in a good agreement with the actual field measurements and could provide quantitative measures of tunnel inflow. The proposed method could be more feasible for a reliable pre-assessment of groundwater inflows in the future tunnel construction projects under heterogeneous geological conditions. Furthermore, the most important factors as well as their combination are introduced for sedimentary rocks.     

Rock brittleness indices and their applications to different fields of rock engineering:A review

Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term.     

模糊综合评判在岩体质量分类中的应用

结合工程岩体具有多样性、可变性、不确定性(随机性、模糊性)和不完全性等特点,从模糊数学综合评判理论出发,建立了多指标性能参数的岩体质量评定模型,通过定量的数值表示评价结果,以使评价指标最优化地接近实际工程地质情况。     

岩体基本质量围岩分级方法介绍及评析

总结了岩体基本质量分级方法的分析思路,给出了岩体基本质量分级方法的详细分级步骤,并通过分析对该围岩分级方法的科学性及可靠度进行了评价。