-
Date submitted2021-12-20
-
Date accepted2024-05-02
-
Date published2024-08-26
A new formula for calculating the required thickness of the frozen wall based on the strength criterion
- Authors:
- Mikhail А. Semin
- Lev Yu. Levin
The study delves into the elastoplastic deformation of a frozen wall (FW) with an unrestricted advance height, initially articulated by S.S.Vyalov. It scrutinizes the stress and displacement fields within the FW induced by external loads across various boundary scenarios, notably focusing on the inception and propagation of a plastic deformation zone throughout the FW's thickness. This delineation of the plastic deformation zone aligns with the FW's state of equilibrium, for which S.S.Vyalov derived a formula for FW thickness based on the strength criterion. These findings serve as a pivotal launchpad for the shift from a one-dimensional (1D) to a two-dimensional (2D) exploration of FW system deformation with finite advance height. The numerical simulation of FW deformation employs FreeFEM++ software, adopting a 2D axisymmetric approach and exploring two design schemes with distinct boundary conditions at the FW cylinder's upper base. The initial scheme fixes both vertical and radial displacements at the upper base, while the latter applies a vertical load equivalent to the weight of overlying soil layers. Building upon the research outcomes, a refined version of S.S.Vyalov's formula emerges, integrating the Mohr – Coulomb strength criterion and introducing a novel parameter – the advance height. The study elucidates conditions across various soil layers wherein the ultimate advance height minimally impacts the calculated FW thickness. This enables the pragmatic utilization of S.S.Vyalov's classical formula for FW thickness computation, predicated on the strength criterion and assuming an unrestricted advance height.
-
Date submitted2023-08-14
-
Date accepted2023-12-27
-
Date published2024-12-25
Modelling of compositional gradient for reservoir fluid in a gas condensate deposit with account for scattered liquid hydrocarbons
In oil and gas reservoirs with significant hydrocarbon columns the dependency of the initial hydrocarbon composition on depth – the compositional gradient – is an important factor in assessing the initial amounts of components in place, the position of the gas-oil contact, and variations of fluid properties throughout the reservoir volume. Known models of the compositional gradient are based on thermodynamic relations assuming a quasi-equilibrium state of a multi-component hydrodynamically connected hydrocarbon system in the gravity field, taking into account the influence of the natural geothermal gradient. The corresponding algorithms allow for calculation of changes in pressure and hydrocarbon fluid composition with depth, including determination of the gas-oil contact (GOC) position. Above and below the GOC, the fluid state is considered single-phase. Many oil-gas-condensate reservoirs typically have a small initial fraction of the liquid hydrocarbon phase (LHC) – scattered oil – within the gas-saturated part of the reservoir. To account for this phenomenon, a special modification of the thermodynamic model has been proposed, and an algorithm for calculating the compositional gradient in a gas condensate reservoir with the presence of LHC has been implemented. Simulation cases modelling the characteristic compositions and conditions of three real oil-gas-condensate fields are considered. The results of the calculations using the proposed algorithm show peculiarities of variations of the LHC content and its impact on the distribution of gas condensate mixture composition with depth. The presence of LHC leads to an increase in the level and possible change in the type of the fluid contact. The character of the LHC fraction dependency on depth can be different and is governed by the dissolution of light components in the saturated liquid phase. The composition of the LHC in the gas condensate part of the reservoir changes with depth differently than in the oil zone, where the liquid phase is undersaturated with light hydrocarbons. The results of the study are significant for assessing initial amounts of hydrocarbon components and potential efficiency of their recovery in gas condensate and oil-gas-condensate reservoirs with large hydrocarbon columns.
-
Date submitted2021-12-15
-
Date accepted2022-09-12
-
Date published2023-08-28
Substantiation and selection of the design parameters of the hydroficated equipment complex for obtaining backfill mixtures from current enrichment tailings
The issue of the influence of the concentration of the solid phase on the reduction of energy costs and specific energy consumption during pulp transportation is considered. The procedure for preparing slurry from the current enrichment tailings is shown. A scheme is given and the operation of a hydroficated unit for thickening and hydraulic transport of backfill mixtures is described. A diagram of the movement of solid particles in one of the units of the complex – a lamellar thickener is shown. The summary table shows the main design parameters and characteristics of the lamellar thickener. A general view of the laboratory setup used for experimental studies with slurry at various concentrations is given. An example of calculating productivity, density and specific load is presented. The dependence of the shear stress on the velocity gradient was determined for various pulp concentrations. Experimental studies of the process of thickening the production of slurry from the current enrichment tailings have been carried out. It was found that the geometric dimensions of the thickener depend on the concentration of the solid phase in the transported mixture. It is concluded that the flow rate of the slurry and the head loss are functions of the rheological characteristics of the viscoplastic slurry and can be calculated from the derived calculated dependencies.
-
Date submitted2021-11-17
-
Date accepted2022-04-06
-
Date published2022-11-10
Method for predicting the stress state of the lining of underground structures of quasi-rectangular and arched forms
- Authors:
- Maksim A. Karasev
- Tien Tai Nguyen
A method for predicting the stress-strain state of the lining of underground structures, the shape of the cross-section of which is different from the circular outline, is considered. The main task of the study is to develop a methodology for assessing the influence of the parameters of the cross-section shape of underground structures on the stress state of the lining. To solve this problem, a method for calculating the stress state of the lining for arched tunnels with a reverse arch and quasi-rectangular forms is substantiated and developed. The methodology was tested, which showed that the accuracy of the prediction of the stress state of the lining is sufficient to perform practical calculations. An algorithm for multivariate analysis of the influence of the cross-sectional shape of underground structures of arched and quasi-rectangular shapes on the stress state of the lining is proposed. Parametric calculations were performed using the developed algorithm and regularities of the formation of the stress state of the lining of underground structures for various engineering and geological conditions, as well as the initial stress state field, were obtained. A quantitative assessment of the influence of geometric parameters of tunnels on their stress-strain state was performed.
-
Date submitted2021-04-20
-
Date accepted2022-04-26
-
Date published2022-07-13
Prediction of the stress-strain state and stability of the front of tunnel face at the intersection of disturbed zones of the soil mass
The article presents a numerical solution of the spatial elastic-plastic problem of determining the stability of the tunnel face soils at the intersection of disturbed zones of the soil mass. The relevance of the study is related to the need to take into account the zones of disturbed soils when assessing the face stability to calculate the parameters of the support. Based on the finite element method implemented in the PLAXIS 3D software package, the construction of a finite element system "soil mass-disturbance-face support" and modeling of the intersection of the disturbed zones of the soil mass were performed. To assess the condition of soils, deformation and strength criteria are taken. The deformation criterion is expressed by the value of the calculated displacement of the tunnel contour in the face, and the strength criterion - by the safety coefficient until the maximum values of the stress state are reached according to the Coulomb–Mohr criterion. The results of the study are presented in the form of histograms of the safety coefficient dependences on the distance to the disturbance at different bending stiffness of the face support structure, as well as the isofields of deformation development. The parameters of rockfall formation in the face zone at the intersection of zones of disturbed soils were determined. The local decrease in strength and deformation properties in the rock mass along the tunnel track should be taken into account when assessing the stability of the tunnel face and calculating the parameters of the support. Within the framework of the constructed closed system, a qualitative agreement of the simulation results with the case of a collapse in the face during the construction of the Vladimirskaya-2 station of the St. Petersburg Metro was obtained.
-
Date submitted2021-03-18
-
Date accepted2021-11-30
-
Date published2021-12-27
Deformations assessment during subway escalator tunnels construction by the method of artificial freezing of soil for the stage of ice wall formation
- Authors:
- Evgenii M. Volokhov
- Diana Z. Mukminova
The work is devoted to the study of the processes of displacement and deformation of the surface during the escalator tunnels construction of the subway by the method of artificial freezing of soils. The features of the construction and freezing technology, the rocks characteristics in which the escalator tunnels made are considered. The data of specially organized, full-scale surveying observations of deformations on the earth surface are presented. The main factors influencing deformation processes in the frozen strata of a layered inhomogeneous rock mass with inclined tunneling are determined, the complexity of the predictive task and the need to simplify the design scheme are shown. The work is focused on the assessment of the least studied geomechanical processes of soil heaving-uplifts and deformations during the periods of active and passive freezing stages. When studying the displacements processes of the earth surface and rock mass, the finite element method and analysis of the obtained data using field observations of displacements were used. A simplified calculation scheme is proposed for modeling, which allows taking into account the uneven influence of frozen rocks of an inhomogeneous layered rock mass with a large inclined tunneling. The satisfactory convergence of the data of field surveying observations on the earth surface and the results of modeling geomechanical processes for the period of active and passive freezing stages is shown. The proposed calculation scheme is recommended for the prediction of deformation at the stages of underground construction, characterized by the development of the most dangerous tensile deformations of buildings and structures on the surface.
-
Date submitted2020-05-25
-
Date accepted2020-06-11
-
Date published2020-12-29
Technological aspects of cased wells construction with cyclical-flow transportation of rock
- Authors:
- Andrei S. Kondratenko
A high-performance technology for constructing cased wells is proposed. Essence of the technology is the advance insertion of the casing pipe into the sedimentary rock mass and the cyclical-flow transportation of the soil rock portions using the compressed air pressure supplied to the open bottomhole end of the pipe through a separate line. Results of mathematical modeling for the process of impact insertion of a hollow pipe into a soil mass in horizontal and vertical settings are considered. Modeling of the technology is implemented by the finite element method in the ANSYS Mechanical software. Parameters of the pipe insertion in the sedimentary rock mass are determined - value of the cleaning step and the impact energy required to insert the pipe at a given depth. Calculations were performed for pipes with a diameter from 325 to 730 mm. Insertion coefficient is introduced, which characterizes the resistance of rocks to destruction during the dynamic penetration of the casing pipe in one impact blow of the pneumatic hammer. An overview of the prospects for the application of the proposed technology in geological exploration, when conducting horizontal wells of a small cross-section using a trenchless method of construction and borehole methods of mining, is presented. A variant of using the technology for determining the strength properties of rocks is proposed. Some features of the technology application at industrial facilities of the construction and mining industry are considered: for trenchless laying of underground utilities and for installing starting conductors when constructing degassing wells from the surface in coal deposits. Results of a technical and economic assessment of the proposed technology efficiency when installing starting conductors in sedimentary rocks at mining allotments of coal mines are presented.
-
Date submitted2017-10-29
-
Date accepted2017-12-31
-
Date published2018-04-24
Risk assessment of accidents due to natural factors at the Pascuales – Cuenca multiple-use pipeline (Ecuador)
- Authors:
- Dzh. Zambrano
- S. V. Kovshov
- E. A. Lyubin
The natural aspects of the accident risk at the Pascuales – Cuenca multiple-use pipeline (Ecuador) are analysed in the paper. The Russian Methodological recommendations for the quantitative analysis of accident risks at hazardous production plants of oil trunk pipelines and oil product trunk pipelines issued in 2016 are used as a methodological framework due to relatively poorly defined evaluation mechanism for natural factors of accidents at oil trunk pipelines in the most widespread international accident risk assessment methodologies. The methodological recommendations were updated to meet the environmental conditions of oil pipelines of Latin America. It was found that the accidents due to natural factors make up approximately 15 % of cases at oil trunk pipelines in Ecuador. Natural geographical features of the areas surrounding the main Ecuadorian Pascuales–Cuenca oil trunk pipeline and its relatively short length allow defining three zones along the line in terms of the accident risk: lowland coastlines, high plateaus, and foothills. Calculations and analysis revealed that the maximum predicted specific frequency of accidents is characteristic of the lowland seaside area. The evidence showed that physical and chemical properties of soils and significant seismic activity are the root causes of failures.
-
Date submitted2015-08-25
-
Date accepted2015-10-24
-
Date published2016-04-22
The modern technology of drilling and casing of well during the exploration of gas hydrates
- Authors:
- N. I. Nikolaev
- Lyu Tyanle
In the paper, the perspectives of exploration and completion of gas hydrate fields and the drilling problems in the gas hydrates of the northwest china are studied. It has been established, that the main reasons of complications in the Muli field are the secondary hydrate formation on the walls of the well and drilling assembly and ice formation inside the set cement during the well drilling and completion in permafrost. It has been shown, that in the areas with permafrost during the drilling of the layers containing gas hydrates, temperature and pressure changes can lead to the dissociation of hydrates. At the same time, pressure increase in the annular space due to the gas release, can lead to the secondary formation of gas hydrates, drill string stuck, ceasing of drilling fluid circulation, which is the reason of serious trouble in the wellbore. The results of the research on the development of drilling fluids compositions, which lower the drilling troubles of permafrost, are presented. Comparative experiments have been conducted to evaluate the effectiveness of thermodynamic and kinetic inhibitors, which prevent the repeated hydrate formation. It has been established, that the kinetic inhibitors have the clear advantage: they have good inhibiting effects even with low amounts of additives. In the laboratory conditions, the researches have been conducted to evaluate the phase equilibrium of gas hydrates during their reaction with the water solutions, containing kinetic inhibitor PVP. A thin clay drilling mud has been developed on the water base, providing the holding of the temperature in the level of –2 °С and its effectiveness for the gas hydrate fields in the PRC has been shown. Casing effectiveness of unstable rocks during the drilling in the conditions of negative temperatures inside the well largely depends on their physical-mechanical properties, composition and the technical indicators of cement materials. The authors suggest the composition of quick-setting cements based on aluminum binding materials. It has been established, that the analyzed compositions have the ability to considerably improve the results of cementing.
-
Date submitted2015-08-25
-
Date accepted2015-10-01
-
Date published2016-04-22
Vibrodiagnostics of the technical state slurry pumps
- Authors:
- V. I. Aleksandrov
- Irzhi Sobota
Analysis of the work hydrotransport systems in processing plants shows that the efficiency of this type transport does not match its technical capabilities: the high laboriousness involved in the operation of the equipment, high hydroabrasive wear of slurry pumps and pipelines, low working life pumps, high metal consumption and energy. The main reason for the lack of effectiveness of hydraulic transport is hydroabrasive wear impellers of slurry pumps, causing rising levels of vibra-tion pumps, reducing the pressure characteristics, general technical state of hydrotransport system and as a result - low pumps life, not exceeding 500 hours of continuous operation. In paper, it is shown that as a criterion of period normal operation slurry pump can be used coefficient of techni-cal state, the value of which is proportional to the relative head, degree of hydroabrasive wear of the impeller and time of continuous operating. The coefficient technical state of slurry pump can be represented as a function of current flow rate and the RMS value of vibration velocity. The re-sults of theoretical and experimental studies used to develop algorithms and techniques express-diagnosis and monitoring of slurry pumps in hydrotransport system, data which indicate the need for routine maintenance of pumping equipment.
-
Date submitted2009-10-15
-
Date accepted2009-12-30
-
Date published2010-09-22
Geotechnical monitoring in cryolite zone. Ecological or industrial safety
- Authors:
- A. P. Popov
The article contains the principal methodological points of the technology of geotechnical monitoring of engineer constructions in the cryolite zone. By way of practical example it was shown the efficiency of its application for reduction of risks in the industrial and economic activities of Gasprom Co by means of creation of numerical models of stability of ground basements and foundations, timely control of mechanical safety of buildings and constructions, qualitative substantiated numerical forecasting and potential variant modeling of aftereffects of technical decisions for stabilization of a situation. Geotechnical monitoring in contrast to the industrial production ecological monitoring is the technology for control of mechanical safety of buildings and constructions at the stages of their designing, construction and exploitation.
-
Date submitted1954-08-02
-
Date accepted1954-10-23
-
Date published1956-01-17
Новый метод расчета неравномерного движения грунтовых вод при наклонном водоупоре
- Authors:
- Unknown
Существуют различные методы гидравлического расчета движения грунтового потока в однородной среде при плоском наклонном водоупоре. Эти методы характеризуются различной степенью приближенности. Так, формулы Г. Н. Каменского [1] не имеют строгого теоретического обоснования. Метод акад. Н. Н. Павловского [2] тоже в известной мере является приближенным, так как по этому методу расчета поверхности равных напоров в условиях плоской задачи рассматриваются как вертикальные плоскости. Метод Н. Н. Павловского можно считать в настоящее время наиболее точным, так как он основан на строгом математическом выводе и его основные положения очень близки к истинной картине движения, когда уклон водоупора и уклон депрессионной поверхности невелики. Предлагаемый в настоящей статье новый метод также является приближенным, но он основан на достаточно строгом математическом выводе. Определение расхода и построение кривой депрессии по этому методу проще и удобнее, чем по методу II. Н. Павловского.
-
Date submitted1947-07-14
-
Date accepted1947-09-29
-
Date published1949-01-11
К вопросу о движении подземных вод в трещиноватых породах
- Authors:
- E. E. Kerkis
Вопросы, связанные с движением подземных вод в трещиноватых породах, до настоящего времени слабо освещены в литературе. В руководствах по гидрогеологии приводится только схема движения воды по трещинам, предложенная еще в 1912 г. А. А. Краснопольским, предусматривающая турбулентный режим движения, выражаемый законом Шези. Между тем в настоящее время имеются расчетные и экспериментальные данные, позволяющие дать более полное освещение условий движения воды в трещиноватых породах, что может иметь существенное практическое значение. В настоящей краткой статье автор приводит произведенные им гидравлические расчеты, основанные на рассмотрении простейшей модели трещиноватой породы с учетом имевшихся экспериментальных материалов. В результате получены выводы, касающиеся режима движения воды в трещиноватых породах и зависимости водопроницаемости их от размеров и густоты трещин.