Disintegration Of Rocks Research Articles

On the mechanism of inrush hazards when Denghuozhai Tunnel passing through granite contact zone

Triggered by excavation or blasting, the underground water and debris may rush into tunnel like a mudflow, which is the essence of inrush hazards in tunnels. Three conditions are indispensible for the occurrence of inrush hazards, namely, material, space and triggering conditions. This paper introduces the inrush hazards of the Denghuozhai Tunnel, and analyses the mechanism of inrush hazards from aspects of material and space conditions. Studies on the lithofacies, minerals and alteration characteristics reveal that the inrush hazards occurred in the contact zone between geodetic granite and tuff. The types and evolution of the altered rocks are identified which indicates an intrusion of volatile-rich magma into the wall rocks at shallow depth under tensile tectonic environment. Albitized, sericitized and clayinitized alteration thus occurred near the contact zone, leading to the formation of tens of meters wide, loose and deeply-buried soft mineral belts, such as sericite, kaolinite and montorillonite, etc. These altered weak zones provide the materials and space for inrush hazards. It is found from the physical, mechanical and hydrological experiments that a high degree of alteration causes swelling, disintegration and argillization of rock and soil, and thus weakens physical and mechanical properties of rocks. This weakening further lowers the triggering threshold of inrush hazards. Therefore, when tunnel excavation approached the altered weak zone, as the weak zone was not identified and no measures were taken to avoid the accidents, inrush hazards were triggered due to excavation disturbance, stress redistribution, blasting vibrations and groundwater drainage. The experiences from these successful cases will be a valuable references and experiences in the design and construction of similar engineering in the future.

Interaction between physical and chemical weathering of argillaceous rocks and the effects on the occurrence of acid mine drainage (AMD)

The disintegration of rocks by weathering plays an important role in the occurrence of Acid Mine Drainage (AMD), which is the environmental problem caused by the exposure of sulfide minerals to water and oxygen. The weathering of rocks is, generally, classified into physical or chemical weathering. However, there are few studies that focus on the complex interaction between physical and chemical weathering of rocks and on the effects of the interaction on the occurrence of AMD. This paper elucidates the complex interrelation between physical and chemical weathering of rocks as well as the progress of AMD through leaching test and weathering test with argillaceous rocks taken in open-cast coal mine in Indonesia in addition to sample analysis before and after the wetting and drying cycle: the rock samples were exposed to oxygen and water during the cycle. The results indicated that the argillaceous rocks which consist of sulfide and/or sulfate caused chemical weathering with micro-cracks on the surface of rocks through the dissolution of soluble iron and sulfur during the occurrence of AMD. Additionally, physical weathering of rocks due to clay minerals was accelerated by chemical weathering with the development of cracks with the occurrence of AMD in the argillaceous rocks containing kaolinite and pyrite. Although weathering of rocks also accelerated AMD, it was concluded that the sulfur content, the form of sulfur and iron in rocks, and the supply of oxygen significantly contributed to the occurrence of AMD.

Subarctic physicochemical weathering of serpentinized peridotite

Frost weathering is effective in arctic and subarctic climate zones where chemical reactions are limited by the reduced availability of liquid water and the prevailing low temperature. However, small scale mineral dissolution reactions are nevertheless important for the generation of porosity by allowing infiltration of surface water with subsequent fracturing due to growth of ice and carbonate minerals. Here we combine textural and mineralogical observations in natural samples of partly serpentinized ultramafic rocks with a discrete element model describing the fracture mechanics of a solid when subject to pressure from the growth of ice and carbonate minerals in surface-near fractures. The mechanical model is coupled with a reaction–diffusion model that describes an initial stage of brucite dissolution as observed during weathering of serpentinized harzburgites and dunites from the Feragen Ultramafic Body (FUB), SE-Norway. Olivine and serpentine are effectively inert at relevant conditions and time scales, whereas brucite dissolution produces well-defined cm to dm thick weathering rinds with elevated porosity that allows influx of water. Brucite dissolution also increases the water saturation state with respect to hydrous Mg carbonate minerals, which are commonly found as infill in fractures in the fresh rock. This suggests that fracture propagation is at least partly driven by carbonate precipitation. Dissolution of secondary carbonate minerals during favorable climatic conditions provides open space available for ice crystallization that drives fracturing during winter. Our model reproduces the observed cm-scale meandering fractures that propagate into the fresh part of the rock, as well as dm-scale fractures that initiate the breakup of larger domains. Rock disintegration increases the reactive surface area and hence the rate of chemical weathering, enhances transport of dissolved and particulate matter in the weathering fluid, and facilitates CO2 uptake by carbonate precipitation. Our observations have implications for element cycling and CO2 sequestration in natural gravel and mine tailings.

DEPENDENCE OF THE ZONE DESTRUCTION THE MASSIVE AROUND MINE WORKINGS FROM THE LIMIT STRENGTH OF THE BREED

In the real work the problem of zonal disintegration of rocks around deep underground workings is considered. The review of new works of foreign scientists in the field is provided. Their main results are reflected, the used methods and approaches are described. In the work the task about distribution of the field of tension around development of round section, in the conditions of an incompressibility and hydrostatic character of a loading on infinity is considered. To be carried out the statistical assessment of a significance of earlier received analytical dependence, the linear look, an arrangement of the middle of the feed zone of destruction measured in the relative to the radius of developments units from ultimate strength of breed on an axial compression. The alternate is constructed statistically the reasonable model of a non-linear look describing dependence of the considered parameters. The comparative analysis with earlier obtained results and the experimental datas is carried out. Statistical significance of non-linear dependence of an arrangement of the feed zone of destruction, from ultimate strength of breed, its convergence with natural data and advantage before dependence of the linear look is shown.

SEISMOGEODYNAMIC FACTOR IN TRIGGERING OF DEBRIS FLOWS ON THE SOUTHERN SLOPES OF THE KODAR RIDGE

Potential triggering of mudflows by geodynamic and seismotectonic factors was assessed for the NE flank of the Baikal rift system, specifically for the junction area of the SW segment of the Chara depression, the Kodar ridge and the Muya-Chara inter-basin zone. The debris flow hazard in the study area is high due to geodynamic and seismotectonic activity and the regional permafrost, hydrological and climatic conditions. In 2001, debris flow damaged the railway section of the Baikal-Amur Mainline (BAM) on the northern shore of the Bolshoe Leprindo lake. To ensure stable railway operations, BAM must be protected from landslides and debris flows. Appropriate preventive actions need to be developed with respect to the correctly assessed current state of the local natural environment, which results from complex interactions between endogenous and exogenous processes. In our study, the Late Cenozoic geodynamics, faulting and seismicity are considered as the most important factors for the occurrence of landslides and mudflows on the southern slopes of the Kodar ridge. The relief in the study area develops in geodynamic conditions predetermined by active stretching of the crust, accompanied by uplifting of the rift shoulder with a large height gradient. The study area is a narrow segment of the zone of dynamic influence of the Baikal rift system. It has a dense network of faults activated in the Late Cenozoic and the fault segments active in Holocene, as deformation caused by the divergent movements of the Siberian and Transbaikalia lithospheric blocks concentrates in this narrow zone. We studied several fault systems, including those activated in the Late Cenozoic, which are related to abundant zones of high fracturing, fragmentation and disintegration of rocks to dust-size particles, accompanied by the most intensive physical weathering in such zones. In the Chara depression and the surrounding uplifts, modern seismicity and paleoseismicity are determined by differentiated movements along the active faults. In the modern and Holocene stages, during and after frequent seismic shocks (including strong ones) in the study area, loose debris materials are inten­sely displaced by gravity, accumulate in negative-relief forms, and provide an important source of solids for debris flows. The Stanovoi Plateau is currently experiencing a period of intensified tectonic and seismic activity, which contributes to favorable conditions for the occurrence of mudflows.

Formation of Waste-rock Drainage Water on Massive Sulfide Deposits of the Urals (Russia)

The waste-rock stockpiles of copper pyrite mines are enriched by sulphide minerals; therefore their dissolution is the reason for the acidic waters formation. Hydrochemical processes responsible for the water quality of the formed waste-rock stockpiles are studied using several sites of the Urals as the examples. Sulphide mineralization causes the sulfate composition of water, iron, aluminum and magnesium to prevail among the cations. The comparison of mine and waste-rock drainage composition shows that waste-rock waters are more mineralized: TDC is 3-5 times higher and the aluminum, iron, copper and zinc concentrations are 4-8 times higher. The composition of rocks forming mine drainage and waste rock drainage is similar, thus it can be hypothesized that the hydrogeochemical processes of mine drainage and of the waste-rock piles waters do not have significant differences. However, the degree of rock disintegration and a temperature gradient in dumps is higher, while the rate of water interchange is lower. The set of hydrodynamic, geomechanical and temperature factors promote the formation of more acidic mineralized waters of the dump body. Computer simulation (Visual MINTEQ ver.3.0/3.1) has shown that with the rate of sulphides oxidation of 3.6·103 mol/hour, the sulphides mass in the dumps would produce acidic leach-water in several hundred years.

Specifics of Studying Crushability of Construction Rocks

Objectives: The existing techniques of studying crushability of rocks are based on the determination of power consumption and aggregate size of the resulting products. Given that during disintegration of the construction rocks it is required to retain rock strength in the crushed stone grains, to improve methodology for crushability assessing is an urgent task. Method: When choosing a method to study crushability of rocks it should be considered that the processes of disintegration in various crushing machines have different mechanisms of action, the most accurate forecast figures are provided by the technique using the destruction mechanism similar to an industrial crusher. A deformation field is created in the entire volume of the body under the load, which leads to a change in the structure and strength of the products formed. In this regard, the strength of crushed stone grains being a final product of disintegration is introduced as an additional indicator that characterizes crushability of rocks. Findings: The article presents the results of studying crushability of construction rocks by different methods. It was found that porosity, particle size, grain shape and loading effort application rate are the factors affecting the strength of crushed stone grains. Mechanical stresses undergone by the rocks during blasting and disintegration result in increased porosity and, consequently, reduce strength. Theoretical dependence of increased strength while reducing the fraction size appears for gabbro-diabases being homogeneous in texture. For granites that are non-uniform in composition and texture there is no unique relationship between the strength and the fraction size. Increased grain cubicity of crushed stone enhances its strength. The study of the crushing kinetics revealed that with decreased loading rate the strength of granite crushed stone having high porosity is reduced, while the strength of the low-porous crushed stone made of gabbro-diabase remains practically unchanged. When choosing a crushing method, either shock or static one, it is necessary to take into account, first, the size of the crushed objects and, second, mineral composition and texture-structural features of the rocks. Improvements: The results obtained are of practical value in selecting rational processing technology and relevant equipment, as well as in the crushing process management to reduce energy costs and improve product quality.

Biologically-initiated rock crust on sandstone: Mechanical and hydraulic properties and resistance to erosion

Biocolonization on sandstone surfaces is known to play an important role in rock disintegration, yet it sometimes also aids in the protection of the underlying materials from rapid erosion. There have been few studies comparing the mechanical and/or hydraulic properties of the BIRC (Biologically-Initiated Rock Crust) with its subsurface. As a result, the overall effects of the BIRC are not yet well understood. The objective of the present study was to briefly characterize the BIRC from both the mineralogical and biological points of view, and especially to quantify the effect of the BIRC upon the mechanical and hydraulic properties of friable sandstone. The mineralogical investigation of a well-developed BIRC showed that its surface is enriched in kaolinite and clay- to silt-sized quartz particles. Total organic carbon increases with the age of the BIRC. Based on DNA sequencing and microscopy, the BIRC is formed by various fungi, including components of lichens and green algae. Using the method of drilling resistance, by measuring tensile strength, and based on water jet testing, it was determined that a BIRC is up to 12 times less erodible and has 3–35 times higher tensile strength than the subsurface friable sandstone. Saturated hydraulic conductivity of the studied BIRC is 15–300 times lower than the subsurface, and was measured to also decrease in capillary water absorption (2–33 times). Water-vapor diffusion is not significantly influenced by the presence of the BIRC. The BIRC thus forms a hardened surface which protects the underlying material from rain and flowing water erosion, and considerably modifies the sandstone's hydraulic properties. Exposing the material to calcination (550°C), and experiments with the enzyme zymolyase indicated that a major contribution to the surface hardening is provided by organic matter. In firmer sandstones, the BIRC may still considerably decrease the rate of weathering, as it is capable of providing cohesion to strongly weathered (and disintegrated) sandstone surfaces. However, only a near-surface zone of the sandstone is stabilized by the BIRC, and additional sources of stabilization (gravity-induced stress, inorganic cement, etc.) contribute to the resistance of the subsurface zone of sandstone exposures.

An analytical and geoarchaeological approach on earthen plaster of 2nd century BCE Karle caves of Western Deccan, India

This study documents a holistic approach, combining mineralogical, geochemical and textural data to characterize the decorative earthen plaster of the 2nd century BCE. Buddhist rock cut caves of Karle in Western India. The analytical examination was carried out by the use of a petrological microscope, Laser particle size analysis, thin section analysis, XRF (X Ray fluorescence), XRD (X Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscope) and Raman spectroscopy in addition to the monitoring of environmental parameters. The results indicate that the local clayey soil, which is abundantly available in the high rain fed western coastal areas, was utilized for the earliest earthen plaster works. The characteristics of the clay seem to have been modified by mixing calcite and an organic adhesive. Rounded sub-angular aggregates derived from disintegration of basaltic rock and rice husk were added to influence shrinkage properties of the plaster. In addition to a better understanding of the technology and composition of ancient India's early earthen plasterworks, scientific data from the analysis was used to plan the composition of restoration plaster.

Rock disintegration selectivity control based on the methods of similarity and dimensions in the fracture dynamics

Rock disintegration selectivity control based on the methods of similarity and dimensions in the fracture dynamics

Modeling temperature field dynamics in post-blasting open pit mines in permafrost

The article discusses the case study of temperature behavior prediction in permafrost rock mass before and after blasting at Kangalass lignite deposit. It is illustrated how the blasting period is related with the temperature behavior in the disintegration of broken rocks. The results are the basis to predict dragline productivity in different seasons and to select efficient scheme for blasted rock removal.

Relics of manual rock disintegration in historical underground spaces and their presentation in mining tourism

Relics of manual rock disintegration in historical underground spaces and their presentation in mining tourism

Investigating the reliability of H/V spectral ratio and image entropy for quantifying the degree of disintegration of weak rocks

Characterization and quantification of disintegration behavior of weak rocks, such as shales, claystones, mudstones, and siltstones, are usually a difficult task because of their extremely diverse nature. These rocks present numerous stability problems along cut slopes around the world because they can change rapidly from rock-like to soil-like materials upon exposure to natural climatic conditions. Engineers often overestimate the design parameters for cut slopes in these rocks when laboratory tests are performed on fresh samples. Adjusting the design parameters for the anticipated amount of disintegration can be problematic because of the complex and time-dependent nature of disintegration behavior. In this study, we investigate the reliability of using microtremor H/V spectral ratio, derived from microtremor signals, and image entropy, obtained from image analysis techniques, for quantifying the varying degrees of disintegration. During 2011–2014, both techniques were used to study disintegration of slopes cut through claystones, mudstones, and limestones along the 80-km stretch of a highway between Bogotá and Tunja in central Colombia. For image analysis, a new algorithm was developed to discriminate between varying degrees of disintegration across the complete color structure of the image, avoiding the gray-scale transformation that is usually time consuming. The results indicate significant correlations between the degree of disintegration of the cut face, the dominant frequency estimated from the microtremor H/V ratio, and the image entropy values, suggesting that H/V ratio and image entropy can be reliable techniques for quantifying the degree of disintegration.

Distribution, Forms and Spatial Variability of Desert Pavements in Arid Western Rajasthan

Abstract A vast area between Phalodi in Jodhpur and Pokaran in Jaisalmer district of western Rajasthan, is occupied distinctly by rocky, shallow gravelly surfaces and occasional hills. These surfaces exhibit quartz and quartzite pebbles, angular, sub-angular and few rounded sandstone gravels, have slightly convex outline and can be best described as desert pavements. Such land features assume significance because of their extent and variability under a dominantly dry aeolian environment. Morphology and distributional pattern of such formations indicate that sediments are either of in-situ origin or may have been transported to a short distance. The present study is based on field level assessment of such surfaces in the above two desert districts. Over much of the area, the profile shows a surficial concentration of gravels followed by thick sand and silt mixed with gravels and then the parent material. There are also occasional rock outcrops of very low relief exhibiting vertical, horizontal and conchoidal pattern of fractures over these surfaces near Pokaran and north of Jaisalmer which indicate disintegration of rocks under extreme diurnal fluctuation of temperature. Such manifestations in the morphology indicate impact of both thermal as well as aeolian processes. In the east of Jaisalmer town near Basanpir and Bhojka, the pavement surfaces are found covered with abundant sub-rounded to rounded pebbles and cobbles. This type of condition would indicate a profound action by fluvial activities followed by wind sorting. Our study found significant spatial variability in the distribution of pavement surfaces, which carried imprints of climatic fluctuations and environment of deposition during Holocene.

Modeling the effect of freezing and thawing for sedimentary rocks

Engineering parameters of rocks mostly depend on internal properties such as mineralogical composition and texture. Physical and chemical processes can cause changes in these engineering parameters. Freeze–thaw is one of the most detrimental phenomena affecting rock properties. This study focuses on the effect of freeze–thaw cycles on the engineering properties of sedimentary rocks. The degree of alteration in the rock, type of cement and the presence of fossils were decisive on rock disintegration during freeze–thaw cycles. Models from two different studies that investigated the weathering behavior under freeze–thaw cycles were applied to the test results of this study. Simple and multiple regression analyses were performed on the test results to predict the UCS values of rocks after 25 cycles, using the results of simply applicable tests at the initial conditions without having to conduct tedious and destructive freeze–thaw tests.

Monitoring of Acoustic Emission During the Disintegration of Rock

Many factors and complexities are involved in breaking rock with conventional methods. Water jet technique is an effective solution to the problems faced in the conventional method. Rock deterioration is the most important step in the mining, civil, mineral engineering, the technology of water jet cutting and disintegration of various material attained continuous growth during the last decades. Water jet is widely used in industrial application such as disintegration of materials and rock, cleaning and removal of surface layers. The literature is reviewed the particular attention to the detection, recording and monitoring of fracture evolution, monitoring of collision healing and creep in rock and other material using acoustic emission. Acoustic emission has been widely used in industries and other various field such as steam pipes and pressure vessels, composites materials, monitor the welding and corrosion progress,metals and also applied numerous structural components. It is a technique to direct monitor defects formation and failure in structural materials. However, it can also provide information on the stress field, fatigue and the fracture pattern behaviour.

Optimization of Gradation and Fineness Modulus of Naturally Fine Sands for Improved Performance as Fine Aggregate in Concrete

Sand is an accumulation of grains of mineral matter derived from the disintegration of rocks. It is distinguished from gravel only by the size of the grains or particles. Sand deposits of varying gradation are available in different regions of the world. The prime use of sand, as fine aggregate is in the manufacture of concrete. As fine aggregate comprises up to 30% of the total volume of concrete, consequently gradation and fineness modulus of sand are among principal factors affecting the performance of fresh and hardened concrete. For the purpose of this study, eight sand deposits were selected from various regions of Pakistan. The grain size distribution was compared with the ASTM gradation limits recommended for concrete. It was revealed that only two sands satisfy the ASTM gradation limits while all the others do not comply being on the finer side. For betterment of the construction industry, a sand optimization technique was developed. The optimization phase consisted of sieving the crusher fines and mixing different fractions of crusher fines with the natural sand in different combinations to get desired sand gradation. The optimized gradation curves matched with the ASTM limits and the optimized fineness modulus reached within the ASTM limits. The concrete made with optimized sands showed up to 39% increase in compressive strength. The composition of mineral constituents was also evaluated through x-ray diffraction and x-ray fluorescence, which indicated that the fine aggregate having higher silica content resulted in concrete with higher strength as compared to the one with higher calcium content. It was concluded that fine graded sands could be used in concreting after optimization that will reduce the huge transportation costs of using coarse sand from far-flung areas.

Modeling the zonal disintegration of rocks near deep level tunnels by gradient internal variable continuous phase transition theory

AbstractThe occurrence of alternating damage zones surrounding underground openings (commonly known as zonal disintegration) is treated as a “far from thermodynamic equilibrium” dynamical process or a nonlinear continuous phase transition phenomenon. The approach of internal variable gradient theory with diffusive transport, which may be viewed as a subclass of Landau’s phase transition theory, is adopted. The order parameter is identified with an irreversible strain quantity, the gradient of which enters into the expression for the free energy of the rock system. The gradient term stabilizes the material behavior in the post-softening regime, where zonal disintegration occurs. The results of a simplified linearized analysis are confirmed by the numerical solution of the nonlinear problem.

Sandstones from the molasse formation in the southern part of the Uralian foredeep

It is shown that sandstones of the Upper Permian—Lower Triassic molasse sequence in the South Ural segment of the Uralian foredeep are graywackes with clasts of predominant cherts, quartzites, quartzite-type sandstones, and less common limestones, polymictic sandstones, basic and silicic magmatic rocks, and serpentinites. Psammites are cemented by corroded calcite; sandstones are frequently enriched in zeolites (analcime and heulandite). According to Dickinson’s concept, the proportions of different types of detrital grains suggest that the considered psammites were formed by the disintegration of rocks of recycled orogen and fold–thrust belt. As compared to the Phanerozic sandstones, graywackes of the molasse have lower mean contents of SiO2, TiO2, Al2O3, Fe2O3, K2O, and P2O5 but ~1.4 to ~3.8 times higher contents of MgO, CaO, MnO, and Na2O. The mean contents of most trace elements in the Upper Permian and Lower Triassic sandstones are lower than in rocks of the upper continental crust. The Th/Sc and Zr/Sc values indicate their predominant petrogenic character. The total REE contents in the studied sandstones vary from 21 to 100 ppm. The highest mean total REE and LaN/YbN values were found in the psammites of the Tatarian stage. This presumably indicates that source areas at that time contained abundant silicic magmatic rocks. Judging from some geochemical features of sandstones, the clastic material was transported over a relatively short distance and did not experience significant chemical differentiation. Data points of psammites in the diagrams Qt/(F + R)–Qp/(F + R) and (Al2O3 + K2O + Na2O)/SiO2, as well as sufficiently low values of the hydrolyzate module, indicate their formation under arid climatic conditions, which is fairly consistent with geological data. Molasse sandstones of the South Ural segment of the Uralian foredeep are one of few geological objects, which demonstrate a good agreement between geological data and reconstructions derived from lithogeochemistry.

Numerical Simulation of Zonal Disintegration of the Surrounding Rock Masses Around a Deep Circular Tunnel Under Dynamic Unloading

A new numerical method, which is called the General Particle Dynamics (GPD) method, is proposed to investigate the zonal disintegration mechanism of isotropic rock masses around a deep circular tunnel subjected to dynamic unloading as well as the stress distributions. A constitutive model based on the GPD method is developed to simulate the zonal disintegration phenomenon in deep rock masses. The number and size of fractured and nonfractured zones are determined using the nonlinear unified strength criterion. It is shown from the numerical results that the dynamic loads and high in situ stress are two dominant factors for the occurrence of zonal disintegration.