Experimental verification of parameter m in Hoek–Brown failure criterion considering the effects of natural fractures

Hoek–Brown failure criterion is one of the widely used rock strength criteria in rock mechanics and mining engineering. Based on the theoretical expression of Hoek–Brown parameter m of an intact rock, the parameter m has been modified by crack parameters for fractured rocks. In this paper, the theoretical value range and theoretical expression form of the parameter m in Hoek–Brown failure criterion were discussed. A critical crack parameter B was defined to describe the influence of the critical crack when the stress was at the peak, while a parameter b was introduced to represent the distribution of the average initial fractures. The parameter m of a fractured rock contained the influences of critical crack (B), confining pressure (σ₃) and initial fractures (b). Then the triaxial test on naturally fractured limestones was conducted to verify the modification of the parameter m. From the ultrasonic test and loading test results of limestones, the parameter m can be obtained, which indicated that the confining pressure at a high level reduced the differences of m among all the specimens. The confining pressure σ₃ had an exponential impact on m, while the critical crack parameter B had a negative correlation with m. Then the expression of m for a naturally fractured limestone was also proposed.     

A quantitative analysis procedure for solving safety factor of tunnel preliminary support considering the equivalence between Hoek–Brown and Mohr–Coulomb criteria

There is a development trend from qualitative towards quantitative analysis for tunnel stability. The widely accepted convergence-confinement method (CCM) provides a quantitative framework for tunnel stability analysis, while the conventional CCM based on closed-form functions is essentially an ideal model without considering the tunnel section shape and rock weight in plastic zone. Herein, based on the CCM framework, a quantitative analysis procedure formulated through numerical simulations for more practical situations was systematically proposed to calculate the safety factor of spray-anchor support system in non-circular tunnel. Besides, similarities and differences between the most widely used Hoek-Brown (HB) and equivalent Mohr-Coulomb (EMC) criteria were considered for practical reference. The proposed method was utilized to conduct quantitative analysis of LDPs, mechanical responses of surrounding rock and safety factors for four typical tunnels, and the consistency between tunnels based on HB criterion (TBHBC) and EMC criterion (TBEMCC) was analyzed. The results indicated that the maximum radial convergence of LDP, plastic zone area, and safety factor of TBEMCC were 34.54%, 37.29%, and 47.71% lower than those of TBHBC respectively. The reasons for differences between results were revealed. The spatial effect induced by the face excavation of TBEMCC was weakened as compared to TBHBC, leading to a drop of LDP. Consequently, the safety factor was underestimated. The method systematically provided an effective tool for quantitative stability analysis and design optimization of support system for an underground excavation.     

Ultimate bearing capacity at the tip of a pile in rock—part 1: theory

This paper proposes a method for calculating the ultimate bearing capacity at the tip of a pile that is embedded in rock, according to the theory of plasticity. The non-linear failure criterion of Hoek and Brown (Underground excavation in rock, The Institution of Mining and Metallurgy, London, 1980) is used. The plastified area is analysed as a two-dimensional medium using the characteristic lines method generalised for non-linear failure criteria. The embedment is simulated using the hypothesis proposed by Meyerhof for piles in soils. The results obtained through the calculations are corrected by applying a shape factor in order to take into account the three-dimensional nature of the pile.     

Combined effects of blasting and geological structure on rock mass stability—a case study from the Marrakech–Agadir highway,Morocco

Bulletin of Engineering Geology and the Environment - The Marrakech–Agadir highway crosses mountainous areas of the Western High Atlas of Morocco with a high risk of slope instability. The...     

Deformation and failure of a tunnel in the restraining bend of a strike–slip fault zone: an example from Hengshan Mountain,Shanxi Province,China

Bulletin of Engineering Geology and the Environment - The Yanmenguan Tunnel runs through Hengshan Mountain in Shanxi Province, China. The mountain is mainly composed of metamorphic rock cut by a...     

The impact of immigration on interregional migrations: an input–output analysis with an application for Spain

Developed countries in general, Spain in particular, have experienced a dramatic rise in the reception of foreign workers in the last decade. Among all the economic and social effects originated by the arrivals of immigrants, the literature has paid some attention to the potential effect that this immigration can produce on the internal migration patterns (the so-called “displacement effect”). This paper proposes the use of a multi-region input–output model of migrations for measuring how the reception of immigrants in one region displaces population among all the regions included in the model. From some basic assumptions, the input–output methodology proposed describes how the arrival of one immigrant in one region i, by the dissemination of internal population from i, generates indirect effects on other region j. To illustrate the methodology proposed in the paper, an empirical application for Spain is also included.     

The synthesis of activated chlorine in an electrodialyzer with a tube ceramic membrane and a titanium–dioxide–manganese anode

The article has investigated the impact of the design of an electrodialyzer with a little soluble titanium–dioxide–manganese anode and a ceramic membrane separating electrode spaces, on the concentration of chlorate–ions when producing sodium hydrochlorite. It has been shown that the location of the anode inside a ceramic membrane makes it possible to obtain sodium hypochlorite without an impurity of chlorite–ions.     

Stress generated by the freeze–thaw process in open cracks of rock walls: empirical model for tight limestone

In mountainous areas, freezing is a prominent phenomenon for weathering processes in rock walls. A freezing front penetrates rock crack networks and causes its propagation. To study the evolution of rock mass stability, a suitable model of stress generated by freezing in open rock cracks is needed. This stress evaluated by the simple volume expansion model in a closed crack is too high to be realistic. In this paper, we present an assessment method for this stress and some results. Different experiments on notched limestone specimens submitted to freeze–thaw cycles were performed. Three different tight limestones (Larrys, Chamesson, Pierre de Lens) were tested. Actually, the stress generated by freezing begins to grow at the top of the notch where an ice plug is created and makes it possible for higher stresses to develop in deeper parts of the notch. Consequently, the stress induced by freezing depends on the geometry of the open crack represented by the notch. This value is, however, limited by the permeability of the surrounding rock matrix. A model of the stress evolution generated by freezing along an open crack was established and its envelope curve, named maximum stress, was parameterized. This maximum stress generated by freezing along the crack is completely defined by knowledge of the pore network of the limestone matrix and the geometry of the crack.     

A novel physico-mechanical parameter for estimating the mechanical strength of travertines after a freeze–thaw test

Bulletin of Engineering Geology and the Environment - Determination of the mechanical strength of stones after freeze–thaw action is important for evaluating the durability of natural...     

Accounting for the linkages of agriculture in Hawaii‘s economy with an input-output model: A final demand-based approach

. Agriculture is not a large contributor to Hawaii‘s economy but despite the recent decline in the sugar industry it is an important sector in terms of its contribution to food supply, income, and employment. Agriculture influences the economy as it procures production inputs from and provides inputs to other sectors in the economy. A theoretically sound input-output framework is suggested for investigating the interdependence between agricultural and other sectors of the economy. This paper also provides a review and identifies shortcomings of other approaches used in estimating the industry‘s contributions to the economy. The non-agricultural final demands accounted for about 20% of total agricultural output, value added, labor income, and employment. The indirect contribution of agricultural final demands and related distribution services to other sectors constituted about 20% of total output and labor income, 22% of value added, and 16% of total employment generated by agricultural final demands and related trade and distribution services. Received: October 1997/Accepted: Febuary 1998     

Is inequality in the distribution of urban facilities inequitable? Exploring a method for identifying spatial inequity in an Iranian city

Achieving spatial equity in the distribution of public facilities has been explored over the last two decades. The direction of these attempts was to offer an integrated index of spatial equity to decrease inequalities between cities. This study seeks to explore an integrated model for spatial inequity measurement (SIM), with a particular focus on inequalities resulting from a) mismatch of population demand (need) and population that can be supported by a facility; b) spatial mismatch of population distribution in relation to facility distribution; and c) mismatch of human deprivation in relation to spatially located “nonenjoyment.” The SIM was examined in 15 kinds of facilities together with different service areas in Hamadan city by integrating geographic information system (GIS) and spatial analysis models. This model identifies and calculates spatial inequities in all city units, in regard to whole facilities, distinct sets of facilities, or an individual facility; it then maps these facilities to determine the areas and the extent to which they experience inequity, for rational prioritization of the distribution of facilities in future planning. The results show that the majority of the city population experienced “nonenjoyment,” indicating a widespread spatial inequity among different groups of people. They also indicated the importance of public facilities in determining the level of inequalities and subsequent deprivation of the poor that can occur from inequitable spatial distribution. This model is an integrated spatial analytical tool that is capable of determining and mapping the level of spatial inequity of all facilities in a disaggregated and aggregated manner for an urban area.     

An introduction to the karst geomorphology of the Bisetun–Taqe Bostan historical region (northeast Kermanshah,Iran) with special emphasis on karst development as a serious threat for the UNESCO World Heritage Site

The Bisetun–Taqe Bostan crushed carbonate massif (northeast of Kermanshah City) is a historical region that includes several famous monuments. Several types of karst features, the surface kind especially, have been developed in the area because of high rainfall in the area, tectonic crushing and high purity of the rocks. The field survey showed that the major karst features are karren, including rillenkarren, trittkarren, and solution runnels. Some of the monument stones by it have been deteriorating. Cavities and caves, solution dolines, and karstic springs are other observed karstic features in the area. Cavities and caves present mostly at intersections of shear faults or joint sets, which are considered the main location of water seepage throughout the limestone mass. Dolines in the region can be divided into two groups including solution and collapse dolines. The first group involves deep and large dolines without surface deposit cover, whereas the second group includes shallow dolines with smaller sizes covered by soil layers. Dolines are not problematic for the monuments because of their relatively high distance from them. There are a number of karstic springs in the study area; the Bisetun and Taq-e Bostan springs are the most important among them. Both springs discharge at a fault surface in vicinity of the monuments. As a part of the present study, deterioration occurring in the monuments due to the karst development was investigated. Moreover, some physical and chemical preservation methods were proposed to protect the monuments.