A practical procedure for the back analysis of slope failures in closely jointed rock masses

Where closely jointed rock masses are encountered in slopes, failure can occur both through the rock mass, as a result of combination of macro and micro jointing, and through the rock substance. Determination of the strength of this category of rock mass is extraordinarily difficult since the size of representative specimens is too large for laboratory testing. This difficulty can be overcome by using a non-linear rock mass failure criterion or by back analysis of such slopes to estimate the rock mass strength. In this paper, a practical procedure and a computer program are presented for the back determination of shear strength parameters mobilized in slopes cut in closely jointed rock masses which obey a non-linear failure criterion rather than a linear one. The procedure shows that the constants to derive normal stress dependent shear strength parameters of the failed rock masses can be determined by utilizing a main cross-section and without a pre-determined value of rock mass rating (RMR). Trials are made for different RMR_m and RMR_s values corresponding to various possible combinations of the constant m and s, which are used in the Hoek–Brown failure criterion, satisfying the limit equilibrium condition. It is also noted that the procedure provides a quick check for the rock mass rating obtained from the site investigations. The method is used in conjunction with the Bishop's method of analysis based on circular slip surfaces. The procedure outlined in this paper has also been satisfactorily applied to documented slope failure case histories in three open pit mines in Turkey.     

Applicability of the geological strength index (GSI) classification for very weak and sheared rock masses. The case of the Athens Schist Formation

 The Athens Schist Formation includes a wide variety of metasedimentary rocks, varying from strong or medium strong rocks such as sericite metasandstone, limestone, greywacke, sericite schist through to weak rocks such as metasiltstone, clayey and silty shale and phyllite. The overall rock mass is highly heterogeneous and anisotropic owing to the combined effect of advanced weathering and severe tectonic stressing that gave rise to intense folding and shearing followed by extensional faulting, which resulted in highly weathered rock masses and numerous shear and/or mylonite zones with distinct downgraded engineering properties. This paper is focused on the applicability of the GSI classification system to these highly heterogeneous rock masses and proposes an extension of the GSI system to account for the foliated or laminated weak rocks in the lower range of its applicability. Received: 5 March 1998 · Accepted: 13 July 1998     

Engineering geological mapping of heterogeneous rock masses in the Northern Apennines: an example from the Parma Valley (Italy)

Most of the geological formations in the Northern Apennines are made up of flysch and tectonic mélanges. A general characterization of the most common rock masses cropping out in the Val Parma is presented in this paper, using the Marinos–Hoek classification based on the Hoek–Brown criterion. Three groups were identified: heterogeneous rock masses essentially controlled by single discontinuities with strengths much lower than the main rock mass (HH); truly heterogeneous rock masses with approximately equal alternations of hard and weak horizons which fail through the weaker materials (TH) and a rock mass in which the majority of the material is weak, tending to soil-like behaviour (WH). A general engineering geological map of the study area is presented, highlighting the spatial distribution of the three different groups.     

Effect of high levels of alkalinity on geotextiles. Part 1: Ca(OH)2 solutions

The adverse effect of high alkalinity solutions on certain polymers has long been recognized by the polymer industry. Most chemical resistance charts and summary tables give an approximate indication of where problems might occur. Lacking, however, is the degree of this effect and the general conditions in which problems might exist. Furthermore, there is no testing methodology to quantitively assess the possible effects.

This paper investigates six geotextiles using alkaline solutions of pH = 12 and pH = 10; and it compares the resulting flow and strength behavior to the as-recieved fabric incubated at the neutral condition of pH = 7. All tests were conducted at the temperature of 25°C (77°F). The flow rate is seen to decrease with the duration of the experiment, and is caused mainly by the formation of a precipitation filter layer on top of the fabrics. The strength data showed a significant reduction in strip tensile strength for both polyester fabrics in the pH = 12 solution. No significant trends were seen in the pH = 10 solution within the 120 days of these tests.

The results point out the necessity of knowing site-specific information about the groundwater (and perhaps soil conditions) so as to properly select a geotextile. Furthermore, the results seem to question the effects of groundwater with moderate alkalinity for longer time periods than evaluated here, and perhaps under elevated temperatures as well. Additional work into these potentially adverse effects seems to be warranted.     

Geochemical characterisation of the outcropping rock masses of the immediate vicinity of wadi el-kaffrein dam site (Jordan)

this paper, the geomechanical characteristics of the discontinuities present in the rock masses, exposed in and around the existing Kaffrein dam site (Western have been investigated for a probable heightening project of the dam in the near future. this purpose, eighteen detailed line surveys were carried out to determine the geometrical and the mechanical properties of the discontinuities. These were located on both the abutments as well as on the exposed rocks near the reservoir area. of the discontinuity orientations, plotted on equal-area stereographic contour nets, have indicated the presence of two sub-vertical joint sets and a one attributed to bedding planes. On the one hand, right abutment rock masses are characterised by low persistence, closely spaced joints that caused formation of small to very small block sizes. On the other hand, exposed rocks on the left abutment reflect the presence of closely to widely spaced, persistent joints which result in small sized blocks. mass Uniaxial Compression Strength (UCS) was determined both in the laboratory and in situ. In situ measurements classified the rock masses as while those measured in the laboratory, classified the rock masses as weak to moderately strong. Low UCS values were assigned to samples taken the left abutment. Such values (UCS<20 Mpa) are believed to be questionable in view of the large difference observed between these values and those from in situ measurements (UCS ? 80 MPa). mass shear strength behaviour of the studied rocks was estimated considering the JRC, JCS of the main discontinuity sets as well as the empirical of Barton and Choubey (1977). The estimated shear strength envelopes relevant to the rock masses of both abutments were similar, and thus, they similar shear strength characteristics. These results indicate the necessity of conducting further laboratory tests on samples to be taken from the left in order precisely to determine the spatiel variation of the shear strength parameters, taking into consideration that future works, regarding the heightening, are to be done on the left abutment. mass quality was determined through the employment of the two widely known geomechanical classification systems: RMR and Q. Both systems a fair to good quality class to the rocks of both abutments. The cross correlation of their results gave a regression equation that is closely similar to of Bieniawski. However, it should be stressed that its validity is applicable, preferably, to the study area. geological and geomechanical investigations, presented in this work, established two main problems that are directly related to the dam ans/or to any developments or works related to it. The first, concerns the heterogeneous nature, from the fracture intensity point of view, of the rock masses of the formation. While the second, concerns the permeable alluvial deposits which cover the reservoir area, through which, an unallowable quantity of water is taking place. conveyed results are believed to furnish valuable technical information regarding the geomechanical behaviour of the exposed rock masses in the vicinity dam. This information could be used to direct or to lead future field &/or technical works in an efficient way in order to pass to the design and execution.     

对IPLV的学习和研究(1):定义解读

通过对GB 50189—2005和GB/T 18430.1—2007的研读,探讨了我国标准中对IPLV的定义。鉴于产品标准作为设计标准的引用和约束标准,认为在研究IPLV时,将产品标准与设计标准分开讨论的研究方式是不可取的。强调了IPLV计算和检测的公式不是IPLV完整的表达式,还应受到GB/T 18430.1—2007标准中其他特定条款的约束。离开这些特定条件,IPLV计算和检测公式不能单独成立。尽管目前的IPLV指标不是评价冷水机组及其系统最完善的方法,但是在更完善的评价方法得到广泛认同之前尚无法被替代,采用COP和IPLV两个评价指标要比只采用其中任何一个要更客观,也更科学。     

Development of a new classification system for assessing of rock mass drillability index (RDi)

The drilling process and its results are affected by various parameters of the rock material and rock mass. The effects of rock material have been emphasized in various studies; however lack of perfect knowledge of rock mass structural parameters may lead to unpredictable results. This paper presents a new classification system for specifying the rock mass drillability index (RDi). For this purpose, six parameters of the rock mass, including texture and grain size, Mohs hardness, uniaxial compressive strength (UCS), joint spacing, joint filling (aperture) and joint dipping have been investigated by physical modeling and rated. Physical modeling in particular has been used for investigating the effects of joint characteristics on drilling rate. In the proposed RDi system, each rock mass is assigned a rating from 7 to 100, with a higher rating corresponding greater ease of drilling. Based on the RDi rating, the drilling rate may be classified into five modes: slow, slow-medium, medium, medium-fast, and fast.     

Stability of large excavations in laminated hard rock masses: the voussoir analogue revisited

Classical assessment of instability potential in underground excavations are normally based on yield and rupture criteria for stress driven failure and on limit equilibrium analysis of structurally controlled failure. While it is true that ultimate failure and falls of ground can be an eventual consequence of stress fracturing and unfavourable structure within the rock mass, the timing of such failure is often controlled by the presence of residual tensile capacity, in the form of rock bridges separating joint segments and fractures and by the mechanisms of clamping and relaxation. Using crack and rock-bridge analogues in conjunction with an updated voussoir beam model, this paper explores the influence of residual tensile strength and boundary parallel relaxation on the failure process. The impact on support design is also examined. In underground hard rock mines with complex geometries and interacting openings, relaxation is identified as a key controlling factor in groundfall occurrence. Empirical stability assessment techniques for underground tunnels and for mining stopes are updated to account for relaxation.     

国外压实机械的发展(一)

介绍国外四大压实机械制造商及各地区市场特点、近年来国外压实机机械产销两旺的发展概况,概括了现代压路机的4项标志及其新技术、新产品的最新发展情况,阐述其发展趋势,并指出各类产品只能互相补充而不能完全替代。     

The Fe3O4-formation by the ‘Ferrite Process’: Oxidation of the reactive Fe(OH)2 suspension induced by sucrose

A mechanism of the formation of small particles of iron oxide in the wastewater treatment system ‘Ferrite Process’ is described. Small particles consisting of the Fe₃O₄−γ-Fe₂O₃ solid solution having slightly higher content of γ-Fe₂O₃ were obtained by the aerial oxidation of Fe(OH)₂ suspension in the presence of a weak dispersing reagent, sucrose, at pH 9.0. The increase of γ-Fe₂O₃ content is caused by a further oxidation of the Fe₃O₄ particles in the course of the reaction. The further oxidation was accelerated below 1000 Å of the particle size. When SO²⁻₄ ion coexisted with sucrose in the reaction medium, the further oxidation was reduced and the treatment of the wastewater was improved. At a temperature interval of 40°–65°C, the formation of α-FeOOH was completely inhibited by a small amount of sucrose and only Fe₃O₄ was obtained.     

民用建筑中的接地(一)接地的基本概念

本文说明了实际工程中正确理解接地符号的内含，有助于对“接地”效果的分析；简述了在工程设计中根据接地电阻值的要求，估算接地体数量；分析了“一点接地”和“等电位”的概念。     

F3权值缩小及高度修正对边坡分级影响的探讨

在边坡岩体分级CSMR中存在不连续面-坡面倾角修正系数F3,其目的是为了考虑不连续面-坡面产状对边坡稳定性级别的影响.考虑到F3的权值过大,现有文献已将其由原来的O～60缩小到0～30.然而F3权值缩小后,边坡高度对CSMR值的影响变大,使得CSMR不再适用于公路边坡等较矮的边坡工程,为了消除这种影响,本文提出在F3权值缩小后高度小于80m的边坡高度不再修正的建议,给出了CSMR计算公式,并用一个实例验证了CSMR在公路边坡中的适用性,说明修正的CSMR法能适用于矮边坡的岩体分级中.     

射流作用下岩石局部渗流压力分布的研究

高压射流辅助破岩在油气井钻井工程中得到广泛应用,其破岩机理还很不明了。本文提出了射流作用下岩石局部范围具有较高渗流压力的思想,并认为该渗流压力大小对射流破岩有重要影响,建立了该渗流压力的计算模型。通过在地面条件下,射流作用于湿砂岩体的多因素数值计算与分析得出:射流的喷射速度大,岩石局部范围内的渗流压力也较大;计算平面的深度位置增加,岩石渗流压力明显减小;压力波(纵波)在岩体中的传播速度变化,对岩石局部范围内的渗流压力影响不大的规律,这对认识岩石在射流作用下的破碎机理有重要意义。