Xu, Shuanhai (Xi’an University of Technology, Xi’an Research Institute of China Coal Technology & Engineering Group Xi’an) | Li, Ning (Xi’an University of Technology) | Cao, Zubao (Xi’an Research Institute of China Coal Technology & Engineering Group) | Liu, Dan (Zhengzhou University)
According to the analysis, there are five types of deformation failure of the slopes along the road which are shallow freeze-thaw creeping of gravel soil slopes in plateau meadow area, cracking of soft rock high slopes by weathering and freeze-thaw cycling, freeze-thaw slump along the planes of consequent rock slopes, freeze-thaw collapse of big colluvial gravel slopes and freeze-thaw slide along basal rock of residual gravel soil slopes. Grassing, water draining, SNS flexible protection net, concrete insert repair, anchored retaining wall or concrete pier, root pile and anti-sliding pile are selected to treat these deformation failures based on different situation.
There is about 200 km distance of Xining-Jiuzhi class II road,which connects Qinghai and Sichuan province, is in a typical alpine environment and it passes through five mountains higher than 4000 meters. This complicated-geological-condition road has several high slopes and ancient landslides.There are many deformation failures, collapses and landslides occur every year along this road because of the rebuilding, freeze-thaw cycling and weathering.
2 Environmental Geological Conditions Along This Road
2.1 Climatic conditions
The weather along this road belongs to plateau mountain climate which is dry, cold, windy and hypoxic. The average temperature is 3.4° and the extreme minimum temperature is -36.2° while the day temperature difference is 16°.The amount of precipitation is 400~500mm which concentrates in from July to September.
2.2 Topography and geomorphology
Along this road, there are four geomorphic unitswhich are alpine mountain landscape, alpine mountain basin landscape, alpine deep valley landform and alpine alluvial plain landscape. The altitude of this area is between 3100m and 4000 m. Both south and north sides of this area are higher than the middle which appears like a valley between two mountains. The altitude difference is about 500 m. Most of the alpine deep valleys areV type while U type valleys are rare. There are alluvial flat and first terrace in the bottom of the valleys. Meadows spread over the high terraces and plateau hills.
Seepage tests under constant triaxial compression stresses were conducted on single granite fractures selected from Beishan with the groundwater in Beishan site as the seepage fluid. Ion concentrations of Al3+ and SiO2 in the exit solution were measured during the seepage tests, and the results were compared with those in the groundwater before test. The mineral morphologies of fracture surfaces before and after test were also examined through SEM scanning. Test results show that there are no obvious variations of SiO2 and Al3+ in the outlet solution during the process of seepage test, while the concentrations of K+ and Na+ increase dramatically and Ca2+ decreases evidently. SEM scanning of the fracture surface also shows that superficial calcification and precipitation occur after the seepage of groundwater. Comprehensive analyses of tests results show that for permanent HLW repository, the long-term effects of groundwater on rock fracture permeability can’t be ignored.
Repositories for high-level radioactive waste (HLW) are located deep underground. The surrounding rockmasses are exposed to the coupled circumstances of crustal stress, seepage of groundwater and chemical dissolution. Long-term reaction between ions in the groundwater and the active minerals in rocks can lead to mineral dissolution, precipitation and chemical element migration. On the other side, the above geochemical behavior and solute migration processwould affect the seepage paths and result in redistribution of stress. Therefore, the long-term permeability evolution of fractured surrounding rockmasses under the seepage of groundwater is one of the key issues to long-term safety prediction of the HLW repository.
long-term safety prediction of the HLW repository. Chemical effect of groundwater has important influences on permeability evolution of fractured rockmass. In recent years, more and more scholars have begun to pay attention to the issue of water-rock reactions. Singurindy & Berkowitz (2003, 2005) conducted a series of laboratory experiments and showed that mineral dissolution and precipitation in carbonate rocks under acid solution seepage would change fracture roughness and affect fracture permeability. Polak et al. (2003, 2004) carried out seepage tests on both limestone and novaculite fractures and verified that the dissolution of minerals at contact points leads to decrease in permeability of novaculite fracture; while for limestone, the intense dissolution process leads to extra flow paths and correspondingly greater permeability in the final stage. Moore et al. (1994) and Tenthorey et al. (2003) conducted experimental studies on sandstone and granite fractures respectively and came to the similar conclusion that under acid solution seepage, fracture aperture decreases due to dissolution of minerals at contact points. However, Liu et al. (1997) and Dijk et al. (2000, 2002) found out that apertures of fractures in carbonate reservoir increase under acid solution seepage. On the basis of previous work of Polak et al., Yasuhara et al. (2004, 2006) and Yasuhara & Elsworth (2008) carried out a series of laboratory tests and came to the conclusion that the competition between dissolution at fracture contact points and the free surface dissolution dominates the fracture aperture variation. Experiments of single granite fracture under constant triaxial stress and chemical solution seepage were conducted by Shen et al. (2010) andYang et al. (2011). The seepage solution is selected as Na2SO4 solution with different pH value to simulate the mineral composition of Beishan groundwater. A preliminary analysis on fracture aperture evolution was carried out with the theory of pressure dissolution and mineral precipitation.
Wang, Wenqing (Helmholtz Centre for Environmental Research – UFZ) | Görke, Uwe-Jens (Helmholtz Centre for Environmental Research – UFZ) | Schnicke, Thomas (Helmholtz Centre for Environmental Research – UFZ) | Kolditz, Olaf (Helmholtz Centre for Environmental Research – UFZ)
This work focuses on the numerical modeling of coupled thermal, hydraulic and mechanical processes in transverse isotropic rock, with specific consideration of parallel computing aspects. We apply the previously developed parallel finite element scheme to analyze a real application, an in-situ heating test carried out in an Opalinus Clay layer of the Mont Terri underground laboratory. The definition of the problem is under the framework of the DECOVALEX-2015 project, an international research collaboration for advancing the understanding and mathematical modeling of coupled thermo-hydro-mechanical (THM) and thermo-hydrochemical (THC) processes in geological systems. Three-dimensional studies of the aforementioned experiment considering transverse isotropic material properties of the Opalinus Clay layer in the test site result in very long computation times using a single computer processor. Results discussed in this work convince us that the present parallel finite method has a good scalability in the context of modeling three-dimensional coupledTHM problems.
Coupled thermal, hydraulic and mechanical processes in rock mass are the phenomena of concern in underground geotechnical engineering such as nuclearwaste disposal and CO2 storage. A better understanding of these coupled processes under long-time conditions is the most important aspect in the context of design and operation of corresponding underground facilities, and it can be realized by numerical modeling (Noorishad et al. 1984; Stephanson et al. 2003; Rutqvist et al. 2005; Wang and Kolditz 2007; Rutqvist et al. 2008; Kolditz et al. 2012). For most applications, especially those requiring three-dimensional simulations, the numerical modeling of coupled THM processes is too time-consuming in computation with regard to a convenience time exposure. Therefore, high performance computing is an essential requirement in such modeling (Wang et al. 2009). In this work, we present a parallel finite element approach for the modeling of coupled THM processes in an in-situ heating test carried out in an Opalinus Clay layer of the Mont Terri underground laboratory (Gens et al. 2007), which is one of the subjects of theDECOVALEX–2015 project. In the test, a heater behaving like a nuclear waste canister applies thermal load at the surface of the hosting drift in the rock, which causes pore pressure change and evolution of deformation in the rock mass (Mont Terri Project). The parallel finite element method is realized by using the domain decomposition method for both the global assembly and the iterative linear solver (Wang and Kolditz 2010). Based upon test data, a threedimensional model is defined. Since the Opalinus clay in the test site is bedded, we consider transverse isotropic material properties in thermal and mechanical processes. The speedup achieved in the presented simulations assures that the discussed numerical parallel scheme provides a promising high performance computing method for the simulation of coupled thermal, hydraulic and mechanical processes observed for in-situ applications.
Tumac, D. (Mining Engineering Department, Istanbul Technical University) | Avunduk, E. (Mining Engineering Department, Istanbul Technical University) | Copur, H. (Mining Engineering Department, Istanbul Technical University) | Bilgin, N. (Mining Engineering Department, Istanbul Technical University) | Balci, C. (Mining Engineering Department, Istanbul Technical University)
One of the most important factors affecting the production rates in quarry mining is the performance of chain saw and diamond wire saw cutting machines. In this study, Shore hardness, Schmidt hammer and uniaxial compressive strength values are used to predict the field performance of chain saw machines. Natural stone quarries are visited in Turkey in order to measure the field performance of chain saw machines. Different natural stone samples are obtained from different quarries for defining the physical and mechanical properties and Schmidt hammer and Shore scleroscope hardness values. The single parameter statistical relationships between Schmidt hammer hardness, Shore scleroscope hardness, mechanical properties and the field performance of chain saw machines are analyzed. Investigations indicate that there are strong relationships between field performance of chain saw machines and Schmidt hammer values, Shore hardness values, mechanical properties of natural stones.
The natural stone industry has unique competitive characteristics that differentiate it from any other industries in terms of technology use and operational characteristics. The chain saw machines, which are the advanced machinery, are able to perform vertical and horizontal cuts for quarrying natural stone mine. These machines are able to cut on natural stones using tools with screw clamp, and work with or without water.
Few studies have been published in the literature related to predicting the performance of chain saw machines. The kinematics of continuous belt type machines (coal cutters, trenchers and chain saw machines) were investigated by Mellor (1976) in terms of working principles and design parameters. Mancini et al. (1992, 1994) analyzed the parameters affecting the chain saw machine performance and the chain cutting was geostatistically simulated. The obtained resultswere compared with field performance of chain saw machines. The in-situ chain saw applications were analyzed by Mancini et al. (2001) in terms of cutting performance, tool wear rate and stone parameters. Primavori (2006) investigated the operational conditions of chain saw machines so as to understand the effective usage of these machines. Copur et al. (2007) carried out full scale linear rock cutting tests in order to analyze the cutting characteristics of chain saw machines. Copur (2010) suggested a deterministic model in order to predict the areal net cutting rate (ANCR) of chain saw machines.
The stability of a large underground powerhouse in the Himalayas has been evaluated. This underground powerhouse cavern constitutes a major component of a Hydro Electric Project in Bhutan. It has experienced a number of instabilities during and after construction. Approximately 5 percent of the bolts in the powerhouse are reported to have failed and the walls of the cavern are continuing to converge, albeit at a slow rate since its completion in 2008. Plans are underway to stabilize this important underground structure. The cavern is located in the complex geological conditions of the Himalayas and close to a high stress thrust zone known as the Main Central Thrust (MCT). This paper evaluates the stability of the powerhouse and discusses measures to strengthen the cavern. Both finite and distinct element analysis are performed to better understand the behavior of the rock mass surrounding the cavern. The results from numerical simulations showing convergences in the walls of the cavern are in fair agreement to those observed at the site. An energy-absorbent support system is recommended for the rehabilitation of the side walls of the cavern.
The construction of underground structures, such as tunnels and caverns in the seismically active region of the Himalayas have generated new thoughts in anticipating the assessing the instability problems posed in such structures. The relatively high tectonic stresses in the area can cause instability in underground structures especially if the rock support requirements do not take into consideration the existence of high stresses in the region.
By virtue of its geographical location on the Southern slope of the Eastern Himalayas, Bhutan is blessed by nature with abundant hydropower potential. Several large hydropower projects are currently under construction in Bhutan and Tala hydroelectric project is the biggest operating hydro power project in Bhutan. The 1020MW hydroelectric project is a joint project between India and Bhutan generating 4865 GWh/yr.
Due to the complex geological conditions in the area the commissioning of the Tala plant was delayed from 2005 to 2008. Druk Green Power Corporation (DGPC) assumed control of Tala in April 2009. The total cost of the project was about 1 billion USD.
Rahmati, A. (Department of mining engineering, Isfahan University of Technology) | Sanei, M. (Department of mining engineering, Isfahan University of Technology) | Faramarzi, L. (Department of mining engineering, Isfahan University of Technology) | Bagherpour, R. (Department of mining engineering, Isfahan University of Technology)
JH classification method is confirmed by the database of up to 6,101 sections of tunnels constructed by Japan Highway Public Corporation. The method can figure out either strength or deformability of rock mass, further appropriating the amount of rock bolts, thickness of shotcrete and size of pitch of steel ribs just after the blasting procedure. Based on these advantages of JH method, in this study, according to data of five deep and long tunnels in Iran, two equations for estimation of value of JH method from Q and RMR classification systems were developed. These equations were able to optimize the support system for Q and RMR classification systems. From data processing, it is pointed out that the JH method for the design of support system in underground working is more reliable than the Q and RMR classification systems.
The most important points in the design of support systems for underground structures can be referred to initial studies to determine the type of rock and the rock mass. Various methods have been proposed for designing and analyzing in underground spaces. The use of these methods requires knowledge of their limitations. Bieniawski (1984) also holds that the quality of input data for design with design requirement is necessary. Experimental methods always have fewer limitations and need tests to that are not costly in the projects. Several methods for the classification of rock masses for the design of support system are presented which include: Barton (1974) Hoek & Brown (1980) and Bieniawski (1984). .
2 Projects Description and Geology
All data used was collected from five tunnels including Golab, Behesht Abad, DashteZahab, Alborz and Sabzkooh Tunnels in Iran. General specifications of tunnels and geological properties of rock mass can be seen in Table 1. Geomechanical properties of rock masses are shown in Table 2.
Most of the discontinuities and joints do not have smooth surfaces and they are covered with random distributed roughness. Finding the effective role of surface roughness on the behavior of discontinuities and on the shear strength of joints makes roughness measurement an important factor that has to be taken into account in geotechnical investigations. These information make the basis for realistic design of underground and surface projects such as tunnel, mines etc. Roughness has various features depending on the type of specimens, size and observation scale. In some cases, different methods of measurement return different results for the same specimen. Therefore, it is necessary to measure the roughness by an appropriate method and to represent it quantitatively in a mathematically adequate way. Quantifying the topography of rippled surface is the main challenge in roughness measurement. This quantifying method should return values which should be used in shear strength formulations for discontinuities. The first step is to measure the roughness topography by an appropriate tool and then their roughness must be quantified by a suitable method. There are different tools measuring the surface roughness. One of these tools is three-dimensional geometric system. Furthermore, several converters can be used amongst which the laser convert is one of them. In this paper, geometric methods used to measure roughness are reviewed. This is followed by a discussion on the various quantitative methods measuring roughness. The 3D laser instrument to record the roughness topography is further explained. Finally, a 2-D profile of a rock joint is scanned and interpreted before and after a shear test.
1.1 Rock mass
Properties of a rock mass are very well related to its joints hydraulic and mechanical properties which these discontinuities themselves are related to the morphology of the rock mass. Roughness as the most important factor of the morphology has a substantial role in the hydraulic and mechanical properties of discontinuities. Due to different results for different measuring methods and techniques for the same rock sample, measuring with precise equipments and quantifying with an appropriate method for the determination of shearing strength and hydraulic properties are essential.
The uniaxial compression constant amplitude fatigue test was adopted to make cyclic loading tests for pre-fractured 30°, 45°, 60° and 90° rock-like model specimens and the corresponding anchored model specimens. It was indicated that the processes of fatigue damage of fractured rock-like specimens can be divided into three stages: fatigue crack initiation stage, fatigue crack propagation stage and fatigue crack rapid propagation stage. Compared with non-anchored model specimen, the plasticity of anchored model specimen was significantly enhanced, and anchored model specimen can bear greater axial strain. The anti-pulling force test analysis was made for the fatigue damage process of anchored model specimen in three stages. During the first and second stages of fatigue damage process, the anchorage body was relaxed, but the integrity of model specimen was intact; in the anterior 80% life cycle of model specimen, the anti-pulling force of anchor was decreased by 20%.
At present, the high-speed railways, highways and other infrastructure constructions in China keep vigorous development and continue to extend to the mountainous areas, whereas the problems in steep and complex rock slope projects are increasingly prominent. These rock slopes along with highways and railways are not only located in the formidable geological environment, but also affected by the long-term impact of cyclic loading of highways and railways. As people start to learn the impact of cyclic loading and attach importance to the security of long-term slope engineering, the research on fatigue degradation for the rocks under the impact of cyclic loading has been one of the hot topics among the researchers in rock mechanics at home and abroad (Ge Xiu-run et al. 2003, Jiang Yu et al. 2004, XU Jian-guang et al. 2008, Wang Guo-yan et al. 2009, M.K. Jafari et al. 2003, S Demirdag et al. 2010, Peckley D C et al. 2009 & Bagde M N et al. 2005).
Joint is the most common weak structural plane in rock slope, but the distribution and strength of joints greatly affect the stability of the rock slope. Anchor is a common approach to reinforce the jointed rock slope, and anchor plays an important role in the crack propagation and deformation of jointed rock. Thus, researches for the effects of anchor on jointed rock will provide meaningful insights for the security, rationality and economy of slope engineering designs. Now, the researches of jointed rock mass and its anchoring effects are mainly focused on the conditions under static loading (Qu Tao et al. 2011 & Yi Yong-liang et al. 2010), but the micromechanical deformation characteristics, process of fracture, fatigue mechanism and its influencing factors, as well as fatigue test of anchored jointed rock under cyclic loading, frequency response of the slope under train load, anti-fatigue design parameters of slope are rarely involved.
The Morsleben repository for low-level and medium-level radioactive waste was established in the old Bartensleben salt and potash mine where several parts, e.g. the southern, eastern, and western part, were partially used for the disposal of waste. To analyse the integrity of the salt barrier in the southern, eastern and western parts in terms of stresses and dilatancy of the salt rock, numerous geomechanical finite-element calculations were performed taking into account the specific geological situation and mining geometry, as well as location-specific material parameters. The barrier integrity at each location was evaluated considering two criteria. The first criterion is related to dilatancy of rock salt: the integrity is guaranteed if rock stresses do not exceed the dilatancy boundary. The second criterion is related to fluid pressure: the integrity is guaranteed if the hydrostatic pressure of an assumed fluid column extending to the surface does not exceed the minimum principal stress at a certain location in the salt rock. The results of the investigations are the basis for evaluating the integrity of the salt barrier for an assumed time period of up to 10,000 years.
The ERA Morsleben (ERAM) geologic repository for radioactive waste was constructed in the former Bartensleben salt and potash mine consisting of several mining parts. The repository was used for the disposal of non heat-generating low radioactive and medium radioactive waste from 1972 to 1998. Especially the southern, the western, and the eastern parts located at the periphery of the mine were used for waste disposal. The emplacement zones are around 500m deep within the rock salt mass. To assess the geomechanical stability of these structures, as well as the integrity of the salt barrier, geotechnical safety analyses are necessary. These analyses are based on geological and engineering-geological studies of the site, laboratory tests and in-situ measurements, and on geomechanical model calculations. Model calculations are the most important part of the geotechnical safety assessment and comprise the geomechanical modelling of the host rock to simulate as closely as possible the conditions of the site and the behaviour of the rock, e.g. geology, repository or mine geometry, initial rock stress, as well as constitutive models and parameters.
In this paper, we outline the work of the International Society for Rock Mechanics Design Methodology Commission’s work in organising the SINOROCK Symposia, in rock engineering design studies, and currently on rock engineering risk. Following a discussion relating to special rock engineering risk conditions, we describe the predictable and unpredictable nature of different projects and highlight ‘black swan’ events. This is followed by an explanation of epistemic and aleatory uncertainty, and how these are both reduced as rock excavation proceeds.An illustrative example of a tunnel driven through box folded strata is included. Uncertainty relating to remedial work for the Mullardoch Dam is Scotland provides a practical demonstration case example of uncertainty and risk.We conclude with a discussion concerning the reduction of rock engineering risk through the development of a corporate memory system together with the use of intelligent monitoring and modelling methods.
1.The Design Methodology Commission of the International Society For Rock Mechanics (ISRM)
The three SINOROCK Symposia (held at the Three Gorges Project Dam Site in 2004, the University of Hong Kong in 2009, and now at Tongji Univeristy in 2013) have been organised by the authors through the ISRM Commission on Design Methodology, together with the assistance of many co-organisers and helpers at the three Symposia venues. The purpose of the SINOROCK symposia is to contribute to the further development of the overall rock engineering design process through the sequential linkage of rock characterisation, modelling and design methods.
During the period 2007–2011, the ISRM Design Methodology Commission researched many subjects relating to the design of rock engineering structures, including the ways ahead for rock engineering design methodologies, flowcharts for the associated modelling and design, the related information required, technical auditing of the modelling and design, and applied the results to a large surface project and a large underground project. The work was significantly supported by Chinese colleagues under the leadership of Professor Qian Qihu and resulted in the book “Rock Engineering Design” (Feng & Hudson, 2011), Figure 1. During the 2007–2011 period,X.T. Fengwas the Commission President and J. A. Hudson was the ISRM President.