Adjoining Rocks Research Articles

Mechanical Properties and Damage Constitutive Model of Thermally Damaged Basalt

Nuclear power is a high-quality clean energy source, but nuclear waste is generated during operation. The waste continuously releases heat during disposal, increasing the adjoining rock temperature and affecting the safety of the disposal site. Basalt is widely considered a commonly used rock type in the repository. This study of basalt’s mechanical characteristics and damage evolution after thermal damage, with its far-reaching engineering value, was conducted by combining experimental work and theory. Uniaxial compression tests were conducted on basalt exposed to 25 °C, 500 °C, 700 °C, 900 °C, and 1100 °C conditions, and acoustic emission (AE) equipment was utilized to observe the acoustic emission phenomenon during deformation. This study was carried out to examine the mechanical characteristics, the sound emission features, the progression of damage laws, and the stress–strain framework of basalt after exposure to different types of thermal harm. As the temperature rises, the rock’s maximum strength declines steadily, the peak strain rises in tandem, the rock sample’s ductility is augmented, the failure mode changes from shear to tensile failure, and cracks in the failure area are observed. At room temperature, the acoustic emission signal is more vigorous than in the initial stage of rock sample loading due to thermal damage; however, after the linear elastic stage is entered, its activity is lessened. In cases where the rock approaches collapse, there is a significant surge in acoustic emission activity, leading to the peak frequency of acoustic emission ringing. The cumulative ring count of acoustic emission serves as the basis for the definition of the damage variable. At room temperature, the damage evolution of rock samples can be broken down into four distinct stages. This defined damage variable is more reflective of the entire failure process. After exposure to high temperatures, the initial damage of the rock sample becomes more extensive, and the damage variable tends to be stable with strain evolution. The stress–strain constitutive model of basalt deformation is derived based on the crack axial strain law and acoustic emission parameters. A powerful relationship between theoretical and experimental curves is evident.

Determination Method for the Strength Model of a Jointed Rock Mass Based on the Geological Strength Index

The mechanical characteristics of materials are the key to numerical calculation, the determination of material parameters of jointed rock mass is conundrum in academia. For the purpose of more efficiently and accurately select the mechanical parameters of the jointed rock masses, in this paper, a new method is proposed which for constructing a numerical model of jointed rock masses, which based on the Geological Strength Index (GSI) and the principles of damage mechanics. With the help of basic concepts of damage mechanics, the joint equivalent coefficient is proposed, establishing the relationship between GSI and joint spacing. The selection way for the mechanical parameters of a jointed rock masses is given in combination with the Hoek-Brown strength criterion. Then, a numerical calculation model is constructed by utilizing 3DEC numerical simulation software to discuss the stability of the adjoining rock under the condition of different GSIs, which is successfully applied to the Wangjialing coal mine project. The numerical results match quite closely with the field conditions, the maximum error is 18%, the minimum error is 5.6%, verifying the rationality and accuracy of this way and providing a new way for the accurate numerical simulation of jointed rock masses.

The Use of Remote Sensing Technology in Geological Investigation and Mineral Detection in Ban Vang area, Kham District, Xieng Khoang Province, Laos

Ban Vang area, Kham District, Xieng Khouang province, Laos is interested by many geologists. Remote sensing analytical results have identified some prospective mineral areas. One of them is the Ban Vang area. On that basis, Indochina Mining Joint Venture Company (IMC) cooperated with the Northwest Geological Division (Ministry of Natural Resources and Environment of Vietnam) to conduct mineral exploration in the Ban Vang area. The research results suggest that the Ban Vang area, Kham District, Xieng Khouang province, Laos has 2 iron ore bodies, 3 copper ore bodies, and potential ore outcrops. The Fe content of the iron orebodies varied from 28.5% to 58.7%. The ore-bearing rocks and the adjoining rocks are gray skarns having a solid structure with the main mineral composition of pyroxene and garnet. The copper content of the copper orebodies ranged from 0.14% to 5.59%. Copper ore bodies’ bedding is inclined to the west with a dip angle from 55o to 85o and thickness from 0.7m to 20.59m. The ore-bearing rocks and adjoining rocks are gray metamorphic rocks (skarn) with massive structure, granule, panidiomorphic, and grain textures. The mineral composition is mainly garnet and pyroxene. This article introduces remote sensing applications of mineral search in the Ban Vang area. The mineral search was conducted by the Northwest Geological Division. In this project, the author is a supervisor of the IMC Company.

СРЕДНОВЕКОВНИТЕ ХРИСТИЯНСКИ ХРАМОВЕ И СКАЛНИ ОБИТЕЛИ ПО ШУМЕНСКОТО ПЛАТО – СВЕДЕНИЯ И ПРОУЧВАНИЯ ОТ ХVІІ В. ДО ДНЕС

The article attempts to present and summarize in a chronological aspect the data and studies related to the medieval Christian churches and monasteries located along the rocky ridge surrounding the Shumen plateau. The sites, that at different times have attracted the attention of many historians and archaeologists, are mostly the abodes associated with the entry of hesychasm into the Bulgarian lands. Evidence has been presented that these were not independent monastic units, but were part of rock hermitages to a monastery or a main church at the foot of the slopes in the ravines of the Shumen Plateau. It can be assumed that the period XIIXIVth century was the apogee of the functioning of the rock monasteries in the Shumen region, but some of them most likely existed in an earlier stage - the Early Bulgarian Middle Ages. The scholarly issues in connection with the model of building of complexes of a main church or monastery and adjoining rock cloisters can be examined in future joined expeditions and research aimed at completing the archaeological map of the Shumen Plateau.

Stress reindexation in coal seams when mining works cross zones of rupturing dislocations

A description of the stress state of the coal seam contained tectonic disturbance with closed edges is presented. The area of the disturbance is shown in the form of an elliptical inclusion and rupturing dislocation with displaced edges. Stress state is defined as a superposition of two solutions on the reference pressure of the coal seam and zone of rupturing dislocation. Changes in the stress-strain state parameters leads to reindexation of the axes with preserving their spatial orientation. This leads to changes in geomechanical state of the coal seams and properties of coal and adjoining rocks when approaching and passing through tectonic disturbances.

INVESTIGATION OF THE GEOMECHANICAL STATE OF SOFT ADJOINING ROCKS UNDER PROTECTIVE CONSTRUCTIONS

The conditions of coal seam mining in the mines of Ukraine have been considered. The problem of conducting coal mining by longwalls in the conditions of soft adjoining rocks, which concerns the protection of mine roadways located near the face, has been revealed. In such conditions, the existing protective constructions are ineffective due to the fact that they yield and get pressed into the soft rocks of the footwall. This indicated the need for research into the geomechanical state of soft rocks of the footwall. According to the results of known studies on the mechanism of rock mass failure around roadways and the data of physical and mechanical properties of the coal mass, which is represented by soft rocks, the correlation dependence has been obtained, the use of which allowed for the determination of the parameters of the rock deformation diagram and the establishment of the stability criterion of footwall rocks under the protection means and stability conditions of the geotechnical system “protective construction – adjoining rocks.” They are the basis of a new approach to ensure the stability of the roadways, which are supported behind the faces, by controlling the stress state in the system “protective construction – adjoining rocks.” This may be the basis for the development of new methods of protecting roadways in conditions of soft adjoining rocks.

Features of rock pressure manifestations with the slice pillarless extraction of the Third potash layer at the Starobin potash salt deposit

Rock pressure manifestations in the development workings and the bottomhole region of the lower longwalls with the slice pillarless extraction of the Third potash layer of the Starobin potash salt deposit were studied. The stability of the development workings and the bottomhole space of the longwalls and the nature of interaction of the bottomhole lining with the adjoining rocks were studied. The intensity of manifestations of rock pressure in the longwalls and the nature of roof subsidence of the bottomhole region and its fall behind the face support were assessed. The nature of the loading speed distribution of the bottomhole lining for the treatment cycle was clarified. The rate of change of the loading before the heading and during this process and the loading rate of the bottomhole lining are taken as the main load support indicators for the treatment cycle. The cyclical nature of the change in the magnitude of these indicators in the interval of 10–12 treatment cycles is revealed. Their dependence on elastic stresses and creep of roof rocks after the formation of a new face is shown. The presence of the dynamic component of the load of the bottomhole lining due to the factor of the speed of the bottomhole movement was established. The influence of the deformation of rocks in the troughs of displacement on the bottomhole lining has been established. At the same time, it is shown that over a time interval of more than 2 years, the intensity of deformation of the rocks is significantly reduced. The possibility is shown how to determine the mean spacing of the secondary rock subsidence of the main roof and to identify anomalies associated with the boundaries of tectonic dislocations, faults and subsidence troughs by analyzing the dynamics of the accumulated deviations from the average of load support indicators. Recommendations have been developed on rational and safe parameters for maintaining the bottomhole region and the development workings of the lower longwalls with the slice pillarless extraction of the Third potash layer.

Asbestiform Minerals of the Franciscan Assemblage in California with a Focus on the Calaveras Dam Replacement Project

ABSTRACT The San Francisco Bay Area is underlain by bedrock of the Franciscan Assemblage, which outcrops in numerous places. A significant portion of these outcrops consists of rock types that contain both regulated and unregulated asbestiform minerals, including ultra-mafic serpentinites, various greenstones, amphibolites, blueschist, and other schists (talc-tremolite, actinolite, etc.). These rocks are a legacy of tectonic activity that occurred on the west coast margin of the North American plate ∼65–150 MY ago during subduction of the East Pacific and Farallon plates. The Calaveras Dam Replacement Project (CDRP), located in Fremont, California, is an example of an area within the Franciscan Assemblage that is substantially underlain by metamorphosed oceanic sedimentary, mafic, and ultra-mafic rocks in a tectonic subduction zone mélange with highly disrupted relationships between adjoining rock bodies with different pressure/temperature metamorphic histories. In order to protect the health of workers and residents in the surrounding area, an extensive effort was taken to identify, categorize, and monitor the types, locations, and concentrations of naturally occurring asbestos at the site. Using a combination of geologic field observations and transmission electron microscopy, energy dispersive X-ray, and selected area electron diffraction analysis of airborne particulate and rock/soil samples, the CDRP was discovered to contain chrysotile-bearing serpentine. It also had as a range of amphibole-containing rocks, including blueschist, amphibolite schist, and eclogite, with at least 19 different regulated and non-regulated fibrous amphibole minerals identified. The extensive solid solution behavior of the amphiboles makes definitive identification difficult, though a scheme was created that allowed asbestos mineral fingerprinting of various areas of the project site.

Providing resistance of protection means on the soft adjoining rocks

Problems of maintaining of development the roadways in conditions of the soft adjoining rocks have been considered. The engineering solution for resistance of rigid protection means by building local reinforced zones under these constructions has been suggested. Combination of protection means and reinforced zones has reduced roof rock subsidence. The operation of protection means and reinforced zones as a holistic construction has been viewed on physical and numerical models. Based on simulation results, the efficiency of deepening of protective means below the footwall, the alternative to which can be creation of the reinforced zones in the footwall rocks, has been established. Factors that have to be taken into consideration when setting parameters of a local reinforced zone under the protective means have been identified.

On-site Monitoring and Comparative Analysis about Surrounding Rock Pressure Variation with Time in Unsymmetrial Loading Tunnel

Bias Tunnes are common seen and it has complicated variation on their surrounding rock pressure. It is crucial for the security and stability of a tunnel to determine the variation law of surrounding rock pressure and on-site monitoring technology. This essay compares the experimental data to the theoretically calculated data of a certain tunnel according to the data from on-site monitoring and theoretical analysis. The result indicates that the real data of surrounding rock pressure of three chosen cross sections is close to the calculated data from grade V surrounding rock. To be specific, the vault and the arch waist are in good agreement. The pressure on the tunnel is obviously unsymmetrial. The data of surrounding rock pressure of arch waist and flank wall on the left side is larger than that on the right side.Also, there is a significant difference between the measured data and calculated data of pressure of horizontal adjoining rock. The horizontal stress of surrounding rock on the bias tunnel is over-released. The measured pressure data on flank wall is much larger than its calculated data.In conclusion, The timbering system should be reinforced in the early stage of construction and the rigidity of timbering system should be chosen carefully. The result of this research can contribute to the tunnel construction design and construction safety in the future.

Structure and tectonics of a Mesoproterozoic ophiolite – Insight from Kanigiri Ophiolite with a mélange zone, southern India

The ~1334 Ma Kanigiri Ophiolite (KO) occurring within the Nellore Schist Belt (NSB) at the Eastern Dharwar Craton (EDC) margin, India provides clues to tectonics of the paleo-ocean outboard of Mesoproterozoic Indian craton. The KO shows a diverse assemblage of fragmentary remains of the then oceanic crust including massive gabbro-anorthosite from the lower part, through a tectonic mélange, to 2–3 km thick slivers of upper oceanic crust with vesicular to pillowed basalt, mafic agglomerate, and mafic to felsic tuff with thin sedimentary intercalation. The mélange consists of up to meter size blocks of mafic igneous rocks and larger rafts of pelagic chert set in a fine grained, weakly foliated mafic matrix showing low grade metamorphism and hydrothermal alteration. The volcanic components of the KO are ultrapotassic to potassic, while the gabbroic rocks show high Ti/V, high Th/Nb ratios, high Y, and enrichment in Th compared to Hf and Ta, suggesting suprasubduction zone oceanic arc setting. Restricted to N-S elongated fault bounded block, the KO shows internal deformation with two sets of folds and tectonic foliation in the upper part and common block-in-matrix structure with gabbroic blocks in the middle part, possibly representing an accretionary wedge. The KO is tectonically juxtaposed against multiply deformed shallow marine succession of the Udaigiri Group (NSB), where second generation folds and crenulation cleavage compare with those in the KO metavolcanics. Post- tectonic granitic stocks of ~1284 Ma age intrude the ophiolitic melange and adjoining rocks of the NSB, suggesting ocean closure and accretionary growth of the EDC margin during the Mesoproterozoic. Components of the EDC margin were fused together during the 1100–900 Ma Rodinia amalgamation with collisional suturing between India and Antarctica. The earlier supercontinent build-up namely Columbia (or Nuna), probably left traces of an archipelago like paleogeographic scenario outboard of the EDC.

Neoarchean tectonics: Insight from the Baijiafen ductile shear zone, eastern Anshan, Liaoning Province, NE China

The North China Craton is one of the major Archean to Paleoproterozoic cratons in the world and oldest craton in China, which preserves a large amount of ancient basement and abundant structures showing the early earth tectonics. The controversy over the Archean tectonic regimes has lasted several decades centering around horizontal and vertical tectonics, the two classical tectonic models for Archean times. Thus, more studies of the early crustal growth and tectonic evolution are requisite for better understanding geodynamic regimes in the early Precambrian. This study provides an example for revealing of Archean tectonics. The NWN-trending, ENE-dipping Baijiafen ductile shear zone is located in the eastern Anshan of the northeastern North China Craton and mainly comprises two types of gneisses, including the Chentaigou porphyritic granitic gneiss and the Baijiafen trondhjemitic gneiss. In this study, we have carried out a detailed study on the macrostructure, microstructure and fabric characteristics of the two main types of deformed gneisses within the shear zone. The ribbon structures formed by intensely elongated quartz grains are widespread in these gneisses. Well-developed mineral stretching lineations and asymmetric fabrics indicate an ESE-directed downward shearing. The quartz c-axis fabric patterns obtained by electron backscatter diffraction technique imply low to middle temperature non-coaxial deformation with active rhomb 〈a〉 slip and basal 〈a〉 slip. Deformation behaviors of minerals and quartz crystallographic preferred orientations demonstrate that the rocks underwent mylonitization at a temperature of 400–500°C under greenschist facies metamorphic conditions. Dislocation creep is the main rock deformation mechanism within the shear zone. Finite strain measurement results suggest that the strain types of the shear zone are generally related to elongate-plane deformation, and the tectonites change from L-S- to LS-type across the shear zone. The strain intensity increases obviously towards east, and the Baijiafen gneiss unit is located within the high-strain zone. Kinematic vorticity values of gneisses indicate that the deformed rocks were produced by steady-state simple-shear dominated general shear. Based on abundant structural evidence and previous studies, we infer that the deformation of the Baijiafen ductile shear zone may have resulted from the downward adjoining rock flow during the sagduction of the banded iron formations and synchronous Archean granite dome emplacement, supporting a vertical tectonic regime in Archean times.

THREE-PARAMETER CREEP DAMAGE CONSTITUTIVE MODEL AND ITS APPLICATION IN HYDRAULIC TUNNELLING

Rock deformation is a time-dependent process, generally referred to as rheology. Especially for soft rock strata, design and construction of tunnel shall take full account of rheological properties of adjoining rocks. Based on classic three-parameter HK model (generalized Kelvin model), this paper proposes a three-parameter H-K damage model of which parameters attenuate with increase of equivalent strain, provides attenuation equation of model parameters in the first, second and third stage of creep deformation and introduces equivalent strain threshold value. When the equivalent strain is greater than the threshold value, the third stage of accelerating creep will be conducted. The three-parameter H-K damage model is used for numerical calculation of finite difference method FLAC3D and deformation features of soft rock with time under high ground stress are described based on diversion tunnel project of Jinping Hydropower Station, of which model parameters can be obtained by back analysis according to measured site data and BP neural network.

Tectonic position of mingling dykes in accretion-collision system of early Caledonides of West Sangilen (South-East Tuva, Russia)

Dykes composed of basic rocks and granite are formed due to interactions between melts in a wide range of conditions, from contrasting compositions and fluid saturation rates to various tectonic settings and processes at different depths. Textures and petrochemical characteristics of the dykes are thus widely variable. This paper is focused on composite dykes observed in the West Sangilen region in South-East Tuva, Russia. The Sangilen wedge is a fragment of the Early Caledonian orogenic structure of the Tuva-Mongolia Massif which evolved in a succession of geodynamic settings, from collision (transpression, 570–480 Ma) to transform faulting (transtension, 480–430 Ma). Intensive tectonic deformation facilitated massive basic-rock and granite magmatism at various layers of the crust and associated heating and metamorphism of the rocks (510–460 Ma). Basic-rock–granite composite dykes were formed in the above-mentioned period in various tectonic settings that controlled conditions of dyke intrusions and their compositions. We distinguish two groups of composite dykes observed on two sites, in the area between the Erzin and Naryn rivers and on the right bank of the Erzin river (Strelka and Erzin Sites, respectively) (Fig. 1). The dykes in both groups originated from one and the same basic-rock melt source. However, mingling of the contrasting melts was carried out by different mechanisms as suggested by the proposed intrusion models. In the area between the Erzin and Naryn rivers (Strelka Site), the host rock of the composite dykes is granite of the Nizhneerzin massif. The mingling dykes are composed of amphibole gabbro and monzogabbro, granosyenite and twofeldspar granite. Contacts between basic and felsic rocks vary from smooth contrasting to complex ‘lacerated’ flameshaped, and gradual transition zones are present (Fig. 6). The dykes were formed at mesoabyssal or abyssal depths, and the subliquidus heat regime was thus maintained for a long time, and even the smallest portions of the basic-rock melt were consolidated through quite a long period of time. As a consequence, indicators of deformation are lacking in the composite dykes, while transition zones and hybridization are present. On the right bank of the Erzin river (Ersin Site), the dykes cut through migmatite-granite of the Erzin formation in the same-name tectonic zone. Contacts with host rocks are transverse. Melanocratic rocks are represented by smallgrained diorite and quartz diorite, and the felsic composite dykes are composed of medium- and small-grained twofeldspar granite and leukogranite. Transition zones, hornfelsing and contact alterations are absent at contacts of all the types (Fig. 8). The composite dykes of this type intruded and emplaced when the shear zone was subject to extension and fragmentation, which predetermined active intrusion of basic and, possibly, felsic melts through conjugated faults. Crystallization of the melts was rapid, and their potential heat impact on the adjoining rocks was thus excluded, as evidenced by the presence of oxygonal chips of igneous and host metamorphic rocks, vein pegmatoid intrusions, and composite dykes of the reticulate-cuspate texture with the dominant basic-rock component. The mingling dykes classified in the first group intruded when the Erzin and Kokmolgarga shear zones were formed at the early stage of the tectonic-magmatic evolution of the Sangilen orogen (510–490 Ma). Intrusions of the basic-rock melts were accompanied by the formation of relatively large massifs of the basic composition, i.e. the Erzin and Bayankol gabbro-monzodiorite massifs, as well as by the occurrence of composite dykes that are abundant in the area between the Erzin and Naryn rivers. In the second stage (460–430 Ma), the composite dykes occurred when the orogen was subject to extension along the system of tectonic zones, the Bashkymugur gabbro-monzodiorite massif was emplaced, and fracture-vein structures, including the dykes, were formed.

Comparison between plate jacking and large flat jack test results of rock mass deformation modulus

The results of two types of loading tests for the determination of the in situ rock mass deformation modulus (Em), namely, large flat jack (LFJ) and plate jacking tests (PJT), which were carried out side by side during the exploratory phase of the Karun 3 hydro-electric project in Iran, have been compared, correlated and analysed. The comparison includes sixteen PJTs and twelve LFJ tests. PJT moduli obtained from displacements measured in depth are much higher than the LFJ moduli and are sometimes even higher than the modulus of the intact rock material. However, this investigation has proved that they can be well correlated with the corresponding LFJ results and reduced by factors established in this comparison. The analyses showed that uncertainties connected to PJT results are caused by the restraining effects of the adjoining rock, and the disturbing effects of blast damage, and also that the scattering of results occurs due to insufficient volumes of rock mass tested. A new empirical relationship for indirect estimates of Em based on the RMR classification scheme is made from field data presented in this investigation and other reliable published data.

First Report of Florencite from the Singhbhum Shear Zone of the East Indian Craton

Metamorphic florencite is being reported from kyanite-rich rocks from the eastern part of the Palaeo- to Mesoproterozoic Singhbhum shear zone. This is the first report of florencite from the Precambrian rocks of the Indian Shield. Host rock of florencite is a kyanite-rich rock (>80 vol%) with small and variable amounts of quartz, lazulite, augelite, and rutile. Florencite forms small (<20 microns) idioblastic-to-subhedral crystals that are included in large kyanite grains. Rarely, florencite replaces kyanite. The florencite has small proportion of crandallite (8.7–11.8 mol%) and goyazite (<2 mol%) components. Florencite of this study is dominated by Ce (~49 mol%) with significant La (~30 mol%) and Nd (~21 mol%). Compared to other florencite occurrences of the world, florencite of the studied rock is impoverished in S, Sr, and Ba and rich in P. Stability of the assemblage florencite-kyanite-augelite-lazulite and the quantitative thermobarometry in the adjoining rocks suggest that florencite was formed during Palaeoproterozoic metamorphism that culminated at theP-Trange of490±40∘Cand6.3±1 kbar. Integrating all the geological features it is postulated that florencite was formed due to metasomatism of some aluminous protolith by infiltration of acidic fluids charged withPO4-3and LREE.

A novel, comprehensive numerical simulation for predicting temperatures within boreholes and the adjoining rock bed

Borehole creation involve complex thermal phenomena such as the injection of a fluid to cool the cutting tool and carry debris to the surface, generation of heat caused by the cutting tool, and the thermal interactions between the flowing fluid and the stationary rock. These phenomena alter the temperature of the rock from its undisturbed state.An accurate characterization of the temperatures within the rock prior to the drilling operation is necessary for resource extraction, geothermal heat conduction calculations, and for paleoclimate studies. Disturbances in the rock temperature can lead to uncertainties in these calculated quantities and in the application of the inverse method.Presently, methods are available which treat the flowing fluid in a simplified manner, often as a stationary medium, and allow estimation of the temperature disturbances in the rock wall. Nevertheless, to the best knowledge of the authors, there are no published studies which fully include the fluid flow in the borehole during the drilling operation and its direct impact on temperatures. Additionally, the impact of the heat generation at the drill head on the temperatures in the fluid and the surrounding rock have not fully been studied.A method is proposed for determining temperatures within boreholes and the surrounding rock both during and after the drilling operation. The method encompasses all the issues listed above. It was discovered that the coolant temperature is dependent upon location within the borehole, and the relaxation time of rock temperatures to their equilibrium values varies with depth in the borehole.

The Excavating Stability Study of a Power Station Underground Plan

In this study, rock stability psychoanalytic theories were concluded, excavation of the underground workshop were done by applying geotechnical common software FLAC3D, then the adjoining rock displacements and transformation rules were simulated and study, and then bolts were used to support the rock, with the study of stress and strain rules and we can analyze and evaluate the effects of the bolting.

Dynamics of toxic heavy metals in different compartments of a highly urbanized closed aquatic system

This paper deals with the dynamics of chromium, nickel, copper and lead among the different components namely water, surface sediments, submerged and free floating macrophytes and fish of the twin manmade lakes, Upper and Lower lakes, of Bhopal (M.P., India). Some basic parameters of water and sediment have also been studied. The basin of the lake system is densely populated and the water is used for various purposes including drinking. Ni and Pb along with nitrate in both lakes are significantly higher than the drinking water quality criteria of USEPA. The concentration of the metals in the sediments is noticeably higher than that present in the adjoining rock, particularly Ni and Pb. There is a significant uptake of metals by the macrophytes (Eichhornia crassipes and Hydrilla verticillata) and fish (Labeo rohita and Oreochromis niloticus) mainly in summer. The fish of Lower lake (O. niloticus) is unfit for human consumption. The data have been statistically treated. Principle component analysis and cluster analysis were performed to define the origin of metals and to assess the relationship among the sites. Overall the Lower lake is more polluted than the Upper lake. In aggregate, the lake system is under an environmental stress due to certain practices.

Laws of Formation and Evolution of Pressure Arch in Coal Mining Adjoining Rock

Based on numerical simulation of computing Software ANSYS, the curve of arching coefficient variation of pressure arch due to actual mining was analyzed aiming to a special mining face, the law of stress transfer and change in surrounding rock was discussed, and the evolving features and characteristics of pressure arch was obtained. The analysis and discussion show the following facts: Arch body will become thicker and stress in the arch body increases with working face’s driving distance increasing; the morphology of pressure arch transits from ellipsoid with long axis in the vertical direction to ellipsoid with long axis in the horizontal direction along the trend of working face; along the tendency of working face, the morphology of pressure arch is a ellipsoid with long axis in the vertical direction.