Water-bearing Rocks Research Articles

Analysis of the main factors determining the value of the specific flow rate of a water well

Purpose of research – numerical characterization of the main factors affecting the value of the specific flow rate of a water well. The relevance of the study is due to the possibility of using the obtained functional relationships to predict the value of the specific flow rate of a water well. Research methods: interpretation of gamma logging curves of water wells, correlation of its results with the core survey data, interpolation of the obtained values over the section area, processing of hydrodynamic well testing materials, comparison of its results with the data of geophysical research, establishment of statistical relationships between the parameters. The results of the study and their application. It was found that the value of the double difference parameter of natural radioactivity of water-bearing rocks statistically significantly correlated with the value of the clay content of core samples, studied in the laboratory way, as well as with the value of water permeability of rocks determined by hydrodynamic tests wells, which allows using this parameter to characterize the filtration properties of rocks aquifer by the value of their clay content. Significant statistical relationship was obtained between the specific flow rate of the water intake well and water conductivity of water-bearing rocks, the parameter of imperfection of the well by the nature of the formation opening, as well as the parameter, numerically equal to the ratio of the well filter length to the value of the double difference parameter of natural radioactivity of rocks of its installation interval. The presence of statistical uncertainty in the relationships is due to the mutual influence of the parameters. The obtained functional relations can be used in the design of wells. Conclusions. During the study the assumption was confirmed that water intake wells with the longest water intake part, equipped in the least clayey and, accordingly, more water-permeable interval of aquifer have the least value of imperfection by nature of formation opening and are able to provide the highest specific flow rate. Such wells are the most effective in operation.

Insights From a Combined Analysis of Acoustic Emission Signals for Water-Bearing Rocks in Four-Point Bending Tests: Failure Mode Classification and Strength Degradation

Insights From a Combined Analysis of Acoustic Emission Signals for Water-Bearing Rocks in Four-Point Bending Tests: Failure Mode Classification and Strength Degradation

Durability analysis and damage constitutive modeling of fiber-reinforced reactive powder concrete of drilling shaft in porous water-bearing rock stratum

The drilling activities at the mining sites in western China generally involve an extremely high drilling depth and complex formation environment, and the external load borne by the drilling shaft lining is also very high. Hence, in this study, fiber-reinforced reactive powder concrete (FRRPC) is proposed as the construction material to enhance the durability of deep drilling shaft structures. Firstly, the main physical and mechanical properties of FRRPC are examined by an orthogonal test method. Then, range analysis and comprehensive balance method are used to determine the optimal mix ratio of FRRPC as cement: silica fume: quartz sand: quartz powder: water: water reducer = 1: 0.25: 1.1: 0.40: 0.0237: 0.031. Next, taking C70 concrete commonly used in drilling engineering of deep loose layers in central and eastern China as a control, the permeability resistance and sulfate resistance of drilling shaft FRRPC in porous water-bearing rock stratum are investigated. The results show that compared with the C70 control group, the relative permeability and corrosion resistance coefficient of FRRPC are increased by 87.7% and 9.9%, respectively. Besides, the FRRPC specimen exhibits significantly better impermeability and sulfate resistance than the C70 control group. Finally, a damage constitutive model of FRRPC under sulfate attack is deduced based on the sulfate resistance test. Overall, this study provides useful insights to boost the application of FRRPC in drilling shafts in northwest China.

Characterization of true triaxial rock bursts in sandstones with different water contents

The rockburst phenomenon occurs in dry red sandstone under high in situ stress, and the rockburst effect is weaker for a water-bearing rock. The rockburst effect on red sandstone with different water contents is analyzed in this paper. A true triaxial testing machine is used to conduct the loading, and acoustic emission recording equipment and a high-speed camera are used to monitor the acoustic signal inside the rock and the rock-caving situation throughout the entire process in order to analyze the characteristics of the acoustic emissions and the ejection form of the rockburst. The results show that rockburst occurs in dry red sandstone and 50% saturated red sandstone but not in saturated red sandstone. The phrase characteristics of the stress–strain curve of the dry rock vary more significantly than those of the water-bearing rock, and the elastic strain energy inside the rock decreases gradually as the water content increases. The double peak of the acoustic emissions curve occurs during the failure process of the dry rock and gradually transitions to a stepped pattern as the water content increases. The ejected fragments of dry red sandstone during the rockburst are abundant and large. The true triaxial test results illustrate the characteristic effect of the rockburst on red sandstone with different water contents, reveal the failure mode and ejection characteristics of red sandstone with different water contents, and demonstrate the influence of the water content on the rockburst characteristics of red sandstone. The results of this study provide a theoretical reference for the study of the rockburst mechanisms of similar hard rocks.

Precursory Analysis of Water-Bearing Rock Fracture Based on The Proportion of Dissipated Energy

In order to better understand the failure process of water-bearing rocks, samples of water-bearing sandstone were tested uniaxially. The failure process and the development of internal cracks were studied through the evolution characteristics of dissipated strain energy and particle flow simulation. In this study, we found that: (1) The presence of water in sandstone results in a reduction in energy storage capacity as well as strength. (2) The dissipated energy ratio curve of sandstone samples and simulated samples’ internal fracture development curve has obvious stages. The dissipated energy ratio turning point and the rapid fracture development point are defined as the failure precursor points of sandstone samples and simulated samples, respectively. In both sandstone samples and simulated samples, the ratio between failure precursor stress and peak strength remains almost unchanged under various water conditions. (3) The ratio of fracture to dissipated energy (RFDE) of sandstone is proposed, and interpreted as the increased number of cracks in the rock under the unit dissipated. On this basis, the fracture initiation dissipated energy (FIDE) of sandstone under different water cut conditions is determined, that is, the dissipation threshold corresponding to the start of the development of sandstone internal cracks. (4) The analysis shows that RFDE increases exponentially and FIDE decreases negatively with the scale-up in moisture content. Further, high moisture content sandstone consumes the same dissipative strain energy, which will lead to more fractures in its interior. The research in this paper can lay a theoretical and experimental foundation for monitoring and early warning of rock engineering disasters such as coal mining, tunnel excavation, slope sliding, and instability.

РАДОН В МИНЕРАЛЬНЫХ ВОДАХ СИХОТЭ-АЛИНЯ (ПРИМОРСКИЙ КРАЙ)

Geological and hydrogeological conditions of 19 occurrences of thermomineral water in the southern Far East of Russia are considered in the paper. Concentrations of radon were measured in waters and those of uranium and thorium in host rocks and secondary minerals. The results were compared with the chemical composition of waters and gases in the mineral springs. It is established that water-bearing rocks are classified into rocks of low and normal radioactivity. The contents of uranium (< 0.56 µg/l) and thorium (< 0.1 µg/l) in the waters are low. Measurements of radon concentration in mineral water springs occurring in Primorye indicate that most of them are weakly radioactive (0.2–1.5 kBq/l), whereas two are moderately radioactive (1.5–7.5 kBq/l). From a medical-balneological point of view, waters in 7 out of 19 springs were defined as radon waters, with four of them classified as nitrogen thermal water and three as CO2-rich mineral water. CO2-rich mineral waters of the Shetukhinskaya group exhibit the highest level of radioactivity. Such nature-made objects reflect the state of the geological environment and can be utilized both for medical purposes and for monitoring a wide range of hydrogeochemical parameters. Based on the analysis of geological conditions and geochemical features of thermomineral water occurrences, the factors that determine the level of radioactivity were identified and general schemes were proposed for the transport of radon to the surface in various geological and hydrogeological conditions.

Ground Slope Stability Analysis

The article analyzes the engineering and geological conditions of the right bank, which is in a state of dynamic equilibrium, of the Oka River. Calculation schemes have been compiled to perform calculations of the total static stability of the slope for two calculated cases in the existing natural state and taking into account the water saturation of the water-bearing rocks, the boundaries of the landslide zone for various cases have been determined. The article identifies possible risks, analyzes the main models of the behavior of the soil base taking into account negative factors, calculates the stability of soil massifs using various known methods. The geometric scheme of the computational model was built on transverse profiles. The width of the calculated area was chosen in such a way that there were no changes in the stress-strain state of the array due to the introduction of artificial boundary conditions along the edges of the finite element grid. The method of calculating stability based on numerical modeling programs by reducing strength characteristics has a number of advantages over the traditionally used methods of calculating stability based on the equations of limiting equilibrium. Based on the results of calculations, the boundaries of the landslide zone for various cases were determined by the method of circular cylindrical sliding surfaces (SAM). A potential landslide zone has been identified, including residential development. Based on the calculations performed, it is proposed to provide alternative measures to ensure the safety of buildings falling into a landslide zone to ensure reliable fastening and minimal impact on the existing slope.

К ВОПРОСУ О МЕХАНИЗМЕ ИЗМЕНЕНИЯ ХИМИЧЕСКОГО СОСТАВА ВОДЫ САМОИЗЛИВАЮЩИХСЯ СКВАЖИН В УСЛОВИЯХ НЕСТАЦИОНАРНОГО РЕЖИМА (НА ПРИМЕРЕ СКВАЖИНЫ ГК-1, ПОЛУОСТРОВ КАМЧАТКА)

The ГК-1 self-discharging well is located in the southeastern part of the Kamchatka Peninsula. The well is part of a network of continuous observations of the groundwater regime, conducted in order to identify and study the hydrogeochemical precursors of strong Kamchatka earthquakes. The article discusses data on changes in the flow rate and chemical composition of well water for the period from 1970 to 2022. The subject of the analysis is the hydrogeochemical effects appearing under the conditions of non-stationary regime arising due to drainage of the pressure reservoir by the well and as a result of changes in bottom-hole pressure. The mechanisms of formation of long-term (decades) and relatively short-term (tens of days) changes in the chemical composition of water at the mouth of the ГК-1 self-discharging well are discussed within the framework of the concepts of water-bearing rocks as a heterogeneous block medium with double porosity.

Improving the pit wall seepage resistance at the V. Grib diamond deposit

Introduction. V. Grib deposit development includes complex dewatering operations, all water-bearing rocks overlying the mining floor are drained. The open pit is mainly flooded by the Padunsky aquifer system. At present, the open pit is being drained by surface dewatering wells together with mine drainage. In total about 7–8 thousand m3 /h of drainage water is pumped out. Setting of the problem. Uncovering a multilayer water-bearing strata characterized by different filtration characteristics of rocks contributes to the formation of pit walls in the Padunsky strata that have not been dewatered. The height of groundwater seepage on pit walls reaches 50 m due to the low conductivity of the Padunsky strata bottom. It is suggested that the Padunsky strata bottom should be dewatered using lateral drain holes built from the pit to the wall benches in areas with no dewatering wells. Methods of research. For pit wall stability improvement, the developed multilayer numerical model of geofiltration is applied to study the use of lateral drain holes built from the pit. The finite difference method in the GMS MODFLOW package was applied for modelling. Research results. It has been found that the operation of 12 lateral drain holes during 1 year reduces the height of groundwater seepage on pit walls by 15–20 m, contributes to the groundwater level decline of the Padunsky aquifer system by 5–10 m on the drainage contour of dewatering wells; water inflow to lateral drain holes will be 810–850 m3 /h. Conclusions. The feasibility of lateral drain holes for the Padunsky strata dewatering intensification in the adjacent rock mass has been established using the method of numerical modeling.

New data on the chemical and isotopic (H, O, C, S, N) composition of mineral waters of the Essentuki deposit

The article presents modern data on the chemical, gas composition, the content of the stable isotopes of oxygen, hydrogen, carbon and sulfur in the natural mineral waters of the Essentuki field. A detailed study of the geological and hydrogeological features of the water circulation territory, their macro components composition, the content of organic matter in the water, temperature conditions and values of δ18ОSMOW, δDSMOW, δ13СDIC, δ18ОDIC, δ34SVCDT, δ13CCO2, δ13CCH4, δ15N revealed the genesis of the aqueous, gas and salt components of the natural mineral waters of the Essentuki field. Established that all natural mineral waters of the Essentuki field are meteoric infiltration waters. The heterogeneous component composition of the natural mineral waters, that circulate in various aquifers, represents the features of the lithological composition of the water-bearing rocks, the degree of openness or closeness of faults and the intensity of reactions in the water-rock-gas-organic matter system.

Detection of groundwater level and heavy metal contamination: A case study of Olubunku dumpsite and environs, Ede North, Southwestern Nigeria

This research presents the result of the application of the PQWT Electromagnetic Groundwater Detector and analysis of heavy metal contamination around an open dumpsite in Olubunku, Ede North, Southwestern Nigeria, which has been in operation for the past fifty years. A PQWT-300S 300 m was used to acquire 8 profiles at the site. The quantitative analysis of heavy metals was conducted for seven available well water samples and five surface soil samples. The water and soil samples (digested) were read on BuckScientific Atomic Absorption Spectrophotometer model 210/211 vap to determine the concentration of Pb,Cd,Cr, Co, and Ni in the samples. As and Hg in the samples were read colorimetrically using a Niesa Spectrophotometer. From the PQWT results, profiles 1,4,5,6,7, and 8 indicate a shallow level of groundwater at a depth of around 30m, which is prone to contamination as most water in the study area is obtained from hand dug wells less than 20m deep. Profile 2 and 3 show contacts that indicate a boundary between fresh basement and well fractured basement, which serves as the water-bearing rock. The HPI scale indicates a high presence of Cd, Hg, Pb, As, and Co in all the samples, which is above the maximum allowable concentration for water. The low scale of Ni and Cr indicates the water is free from Ni and Cr contamination. In the soil, the Igeo scale of Co, Ni, Cd, Pb, and Hg are higher than the maximum allowable concentration, while As and Cr are very low and therefore pose no threat. Chromium is generally low in both the soil and water samples analyzed, while Co, Cd, Hg, and Pb are high above the prescribed scale in both soil and water samples.The groundwater depth in the study area is predominantly at a shallow level of around 30m. The high conductivity of the top shallow level is suspected to be due to contamination by leachates from the dumpsite. The soil and groundwater in and around the investigated dumpsite may be polluted. The study has indicated the vulnerability of the unconfined shallow aquifer underlying the predominantly clayey sand and the effectiveness of PQWT EM in delineating groundwater zones in the basement complex.

Hygienic assessment of manganese content in household and drinking water supply sources of the Vladimir region

Introduction. One of the most important tasks to ensure the sanitary and epidemiological well-being of the population of the Vladimir region is to provide it with high-quality drinking water. Due to the territory of the region to be partially associated with known hydrogeochemical anomalies of excess manganese content in groundwater, a hygienic assessment of the water of economic and drinking sources was carried out according to the content of this element. Materials and methods. The paper presents the data of own research of the Department of Biology and Ecology of the Vladimir State University named after A.G. and N.G. Stoletov for 2021. During this period, the authors of the work examined about 110 samples of water from the household and drinking centralized and non-centralized water supply of the Vladimir region. Water samples were taken in the largest settlements (these are district centers, regional cities and large district settlements) and from drinking water sources of individual farms located in the territory of the region in various districts. The manganese content in water was determined on the analyzer “Fluorat-02-5M” according to HDPE F 14.1:2:4.188-02. Results. The drinking water of the centralized water supply of the Vladimir region in terms of manganese content was established to meet regulatory requirements and be safe for the health of the resident population. In all samples of drinking water, the concentration of manganese is below 0.1 mg/dm3. At the same time, water from underground sources of non-centralized water supply has in some cases an excess of manganese (from 2 to 7 MPC), which is primarily due to the specifics of the geochemical composition of the water-bearing rocks of these territories. Conclusion in order to provide the population of territories using underground water with a high content of manganese, it is necessary to build local modular water treatment plants using modern methods of non-reactive de-ironing and demanganation and using effective modern equipment and filtering materials.

Mechanical Properties Damage, Fracture Evolution, and Constitutive Model of Siltstone under the Effect of Moisture Content

In order to study the weakening mechanism of mechanical properties and the evolution of fracture of water-bearing rocks, cylindrical standard siltstone samples with four moisture contents (0, 2.85, 3.87, and 4.25%) were prepared, and the mechanical properties, damage mode, AE characteristics, and fractal law of water-bearing rock samples were studied by means of uniaxial compression test and acoustic emission (AE) monitoring technique, and based on the test findings, a constitutive model of the entire process of rock deformation and damage under uniaxial compression was built with different moisture content of rock. The results show that with the increase of moisture content, the peak stress, the stress threshold of void compaction stage, and the stress threshold of elastic stage of the rock samples decreased linearly, elastic modulus decreased exponentially as a function, and the peak strain, the strain threshold of void compaction stage, and the strain threshold of elastic stage increased linearly. The higher the moisture content, the weaker the AE signal intensity and the smaller the AE count value. From dry to saturated, the damage form of rock samples gradually transitioned from predominantly tensile damage to predominantly shear damage. The fractal dimension of the broken block linearly decreases as the moisture content rises. The model constructed in this paper has good applicability to the deformation characteristics of water-bearing rocks under uniaxial compression before the peak stress; it especially can express the rock void compaction stage, but it cannot accurately describe the postpeak deformation characteristics.

Analysis of Surrounding Rock Pressure of Deep Buried Tunnel considering the Influence of Seepage

This paper takes the surrounding rock of deep tunnel as the research object and considers the action mechanism under the influence of seepage. Based on the Mohr-Coulomb criterion, the stress mechanism of surrounding rock of deep buried tunnel is analyzed by a convergence constraint method. Based on the elastic-plastic solution, the nonlinear elastic-plastic solution of the interaction between surrounding rock and lining structure considering the effect of seepage force is proposed, and the radius of surrounding rock plastic zone is obtained. The relationship between surrounding rock stress and displacement, radial deformation of lining, and support reaction force was observed. At the same time, considering the effects of seepage, strain softening, and intermediate principal stress, the surrounding rock is divided into a plastic residual zone, plastic softening zone, and elastic zone, and the stress distribution expressions of the plastic zone and each zone of surrounding rock of circular tunnel are derived. The results show that with the change of nonuniform permeability coefficient, the seepage shows anisotropy in different directions, and the closer to the horizontal or vertical direction, the more obvious the influence of nonuniform permeability coefficient on pore water pressure distribution. Seepage and material softening have different effects on the distribution of surrounding rock stress field and the size of plastic zone. Material softening is more unfavorable to the stability of surrounding rock than seepage. The intermediate principal stress coefficient has a significant impact on the tangential stress and plastic zone of surrounding rock. When the intermediate principal stress effect is not considered, the calculation results are relatively conservative and cannot give full play to the strength of surrounding rock effectively. The research conclusion can provide a theoretical reference for studying the stability of surrounding rock in tunnel excavation under water-bearing rock.

Time-Frequency Characteristics of Acoustic Emission Signals on Water-Bearing Sandstone Specimen Subjected to Conventional Uniaxial Compression

This paper presents an experimental investigation of acoustic emission (AE) time-frequency characteristics of a water-bearing sandstone specimen in a conventional uniaxial compression test. The main achievements are as follows: (1) The violent fluctuation of AE time domain parameters indicates that the water-bearing sandstone specimen is about to be destroyed. This characteristic provides a theoretical basis for predicting the failure of water-bearing rock in engineering practice. (2) In the elastic phase, the AE b value is the lowest but has a sudden increase after falling into the steady crack propagation phase. In the unsteady crack propagation phase, the AE b value is further increased. This characteristic is of great indicative value for predicting the failure of the water-bearing sandstone specimen. (3) The difference of dominant frequency among the three key points is very small, indicating that the crack initiation and propagation of the water-bearing sandstone specimen has a certain stability in the damage and failure process. But, the two-dimensional frequency spectrum structure of AE waveform signals shows that the closer to failure, the more the number of the frequency spectrum structure peaks. (4) The energy of AE signals is mainly concentrated in the first three frequency bands. The closer to failure, the more the energy proportion of the first three frequency bands is reduced; conversely, the energy proportion of the latter five frequency bands is increased, which leads to more complexity of the failure modes of the water-bearing sandstone specimen.

Dynamic Response and Damage Regularity of Sandstone with Different Moisture States under Cyclic Loading

In the process of geotechnical engineering excavation, wet and water-filled rock masses are inevitable. To obtain the mechanical properties of these rocks, indoor tests are required, and most of the rock tests rock tests are dry or nearly dry. They cannot really reflect the true nature of the rock, let alone its nature under a dynamic load. The rock was repeatedly impacted during the blasting excavation process. To determine the mechanical response characteristics and damage evolution of rocks with different moisture states under cyclic dynamic loads, rock samples with three saturation levels were prepared. In the experiment, the Hopkinson pressure bar equipment was utilized to perform five cycles of impact with the same incident energy, and the dynamic response of rocks with different impact times was recorded. Nuclear magnetic resonance technology was employed to obtain the change law of the pores of rock specimens after impact, and the cumulative damage rules of rock were combined with the fractal theory. From the experiments, it can be observed that the stress-strain curves of all rock samples are similar, in that they all have stress addition and unloading stages. The peak stress is proportional to the impact time and moisture content, whereas the opposite is true for the peak strain. After the impact, the small and large pores closed and increased, respectively. The porosity and porosity change rate increased with an increase in the impact time. With an increase in moisture content, this trend is more obvious. It can be observed via magnetic resonance imaging that the internal fractures of the water-bearing rock are obvious after multiple impacts. In particular, the saturated rock specimens exhibited severe damage. Fractal analysis of the NMR figures revealed that after three impact times, the fractal dimension change in the water-bearing rock samples was not obvious. This phenomenon indicated that a macro gap appeared. The fractal dimensions of the dry rock samples continued to increase, and the internal damage was less obvious.

Mechanical Behavior and Impact Resistance Tendency of Coal Mass with Different Water Content

As a major hidden danger of mine safety production, the impact resistance tendency of rock seriously restricts the safety and high yield of coal mine. At the same time, as one of the puzzles of rock mechanics, it has been perplexing many domestic and foreign scholars since the recorded rock burst in South Stafford coal mine in 1738. At present, this research is relatively weak; so, it is different for economic and social benefits. The study of the impact resistance law and the antishock measures of water-bearing rocks are extremely meaningful. In order to deeply explore the impact resistance law of rock with different water content and the antishock support measures after roadway excavation, based on the previous research results of the previous research, the impact tendency of different coal samples was firstly tested by coal uniaxial compression experiment, judging and then calculating the damage characteristics of rock with different water content according to the obtained data, as one of the judgment basis of the impact law of coal mine. Secondly, according to the experimental data, the energy evolution characteristics are calculated and analyzed with the graph. Finally, the impact tendency of the rock under different moisture conditions is obtained.

Failure analysis of water-bearing rock under direct tension using acoustic emission

The potential mechanism responsible for water-weakening effects on the direct tensile failure of rocks remains poorly understood due to the difficulty of experimental control and the occurrence of multiple water-rock interactions. To obtain such knowledge, a series of direct tension tests of marble rock under dry, natural and saturated conditions, coupling with the acoustic emission (AE) signals monitoring, were conducted. Some indices, such as AE energy, the ratio of rise time to amplitude (RA) and the average frequency (AF), were unitized to investigate the micro failure process of marble rock. Test results show that the tensile strength of marble rock significantly decreases with the increase of water content, characterizing variable fracture surfaces. The cumulative AE energy released in each loading stage (i.e., entire loading stage, loading stage before peak stress, and loading stage after peak stress) significantly decreases with growing water content. The greater reduction rate of cumulative AE energy released before peak stress can be result from prominent frictional weakening effect induced by water. Also, investigation of crack classifications and failure patterns based on the polarity and AE parameter methods suggests that, the number of tensile cracks, which dominates the progressive failure process of rock under direct tension, is positively correlated to the water content. The crack classification criterion described as the optimal ratios of AF and RA values in AE parameter method is found to be affected by water content. Finally, the primary mechanism for the marble rock deterioration under direct tension is friction weakening, and the effect of pore water pressure is very limited due to the loading regime. The friction weakening effect is largely attributed to the water film but not likely to the mineral dissolution.

Geochemistry of Brines and Oil Occurrences in the Udachnaya Kimberlite Pipe (Siberian Platform)

Abstract —Results of a geochemical study of brines and oil occurrences in the Udachnaya kimberlite pipe are presented. Like other intrusions in the Daldyn–Alakit diamondiferous region, this diamond deposit is a unique cryohydrogeologic microstructure differing from the host sedimentary rocks and other diamond pipes of the Yakutian diamond-bearing province. Two waterlogged zones distinguished in the section of orebodies at the explored depths of the deposit correspond to the upper and middle Cambrian aquifers. Predominantly acidic (average pH = 5.5) Cl–Ca and Cl–Ca–Na brines with TDS from 94.3 to 391.3 g/dm3 are widespread within the orebodies and host rocks. The brine mineralization and contents of major salt-forming components increase with depth, to the horizon at the -365 m elevation, where TDS reaches 391 g/dm3, while below, at the –650 m level with noted hydrogeochemical-field inversion, TDS is 253 g/dm3. The mineralization of Cl–Ca, Cl–Ca–Na, Cl–Ca–Mg, and Cl–Ca–Mg–Na brines in the upper Cambrian rocks varies from 102.9 to 192.9 g/dm3, and the pH values, from 4.9 to 6.2, averaging 5.6. Among the microcomponents, the highest average concentrations (mg/dm3) are found for Br1292.8 > S875.7 > Sr453.7 > Fe79.7 > Li53.4 > B32.7 > I13.3 > Si10.8 > Mn6.4 > Se3.6 > Rb2.3. The values of genetic coefficients vary widely: The rNa/rCl coefficient ranges from 0.18 to 0.31; rCa/rMg, from 1.03 to 3.60; Ca/Cl, from 0.2 to 0.3; and the integrated metamorphism index S (according to S.L. Shvartsev) varies from 193 to 277. The middle Cambrian rock complex, containing more saline brines, has been examined in much more detail. It hosts Cl–Ca, Cl–Ca–Na, Cl–Ca–Mg, and Cl–Na–Mg brines with TDS from 94.3 to 391.3 g/dm3 and high average concentrations (mg/dm3) of microcomponents: Br2224.9 > Sr1024.9 >S500.1 > B202.9 > Li147.1 > Fe97.0 > I33.2 > Rb11.4 > Si9.6 > Se9.5 > Mn3.6 > Ni1.7. As compared with brines in the overlying rocks, the middle Cambrian brines show a wider variation in element ratios: rNa/rCl from 0.14 to 0.34, rCa/rMg from 0.66 to 9.71, and Ca/Cl from 0.03 to 0.45. These brines are also characterized by a significantly higher metamorphism grade, which is indicated not only by the rNa/rCl and rCa/rMg ratios but also by the S index varying from 278 to 316. The composition of stable isotopes δD and δ18O) and dissolved inorganic carbon δ13C) of the brines was investigated. The studied waters are assumed to be of sedimentary–metamorphic origin. Their isotopic composition reflects the climatic conditions existing at the time of their burial, which were probably aggravated by the contribution of the oxygen isotope exchange with water-bearing rocks. The δ13C values of carbon dioxide dissolved in water allow an inference about its biogenic origin. The biogenic carbon isotope exchange is governed by the relationship between methanogenic and SMT processes. Analysis of the 87Rb/86Sr and 87Sr/86Sr isotope ratios of the studied brines has revealed affinity between the isotopic compositions of waters in the Cambrian deposits and in ancient seawaters. The mass chromatograms of saturated-hydrocarbon (HC) fractions show at least two individual types of oils and malthas (naphthides). The third variety resulted from their mixing at different stages of migration. The fourth is from the contact zone; it changed during the explosion of kimberlites. The first, most common, type of naphthides (“postexplosive”) is similar in all geochemical parameters to oils from the Nepa–Botuobiya anteclise, in particular, to those from the Mirnyi arch. Oils of the second (pre-explosive) type are found only in the Udachnaya Formation, within the depth range 1130–1430 m.

Dynamic Compression Characteristics and Failure Mechanism of Water-Saturated Granite

For Fangshan granite in Beijing, the static compression and dynamic compression tests have been carried out separately under natural air drying and water saturation. It was found that the dynamic compressive strength of water-saturated granite is higher than that of air-dried granite, which is contrary to the result that the strength of water-saturated rock is lower than that of air-dried granite under static load. Furthermore, under the medium strain rate condition, when the strain rate is 85 s−1, the dynamic strength of natural air-dried granite could be increased by nearly 0.5 times compared with its static state. The dynamic strength of water-saturated granite could be increased by nearly 1–2 times compared with its static strength, which shows that water-saturated granite has stronger strain rate sensitivity than natural air-dried granite. Meanwhile, under impact loading, from the perspective of water-bearing granite the Bernoulli effect of fluid, the adhesion effect of free water and the Stefan effect of fluid in water-saturated granite were revealed, and found to be the essential reasons affecting the dynamic strength of water-saturated granite. The dynamic strength in different water-bearing states in the range of medium strain rate could then be analyzed in depth, providing a certain reference value for the strength design of water-bearing rock engineering.