Engineering Geological Conditions Research Articles

Microzonation of Ground Motion Parameters in Shangluo City

This paper studied the regional seismic tectonic characteristics, regional seismic activity characteristics, the near-field seismic tectonic characteristics, near-field earthquake activity characteristics about the site of Seismic Microzonation in Shangluo City, seismic belts and potential seismic source zone were divided, calculating the seismic risk analysis of the bedrock of the site, surveying engineering geological conditions in the site, carrying out the seismic response analysis of the site, and zoning the ground motion parameters of the site. The above results provide a basis for the seismic fortification of the proposed general engineering in the site.

Collapse risk assessment of deep-buried tunnel during construction and its application

The hazard of tunnel collapse is a key factor restricting the excavation progress and safety of the tunnels excavated by drilling and blasting. To control this construction risk, a new risk assessment method of tunnel collapse involving case analysis, advanced geological prediction, and Dempster-Shafer (D-S) evidence theory is put forward. At first, after analyzing the typical tunnel collapse cases, 11 influencing factors were adopted as the risk evaluation indices from the natural environment, engineering geological conditions, design and construction, organization and management, as well as advanced geological prediction. Further, the risk indices and their corresponding ratings are calculated to establish the assessment index system. Secondly, for calculating the index weights, the Euclidean distance based on the number of intervals is applied for obtaining the basic probability of each index belonging to each risk grade. Furthermore, the index weights are determined depending on the degree of similarity and support between the indices. Thirdly, the tunnel collapse risk level is obtained based on the D-S fusion rule. In this way, the theory and technical system of risk control of tunnel collapse are established. Finally, the established risk assessment method of tunnel collapse is successfully applied to the Yuxi tunnel. The consequent result is in perfect accordance with the practical condition which suggests that this approach is reliable and practical. This study provides references for other similar tunnel constructions.

Study on Refined Back-Analysis Method for Stress Field Based on In Situ and Disturbed Stresses

Due to uncertainties in the geological evolution process, engineering geological conditions, and nonuniqueness of the solution for in situ stress regression analysis, stress field regression has always been a difficult issue in geotechnical engineering. In view of this problem, a refined back-analysis method for the stress field is proposed in this study based on in situ stress and disturbed stress. First, the in situ stress and disturbed stress in the unloading zone are measured by field tests. The process of geological evolution and excavation disturbance is numerically simulated. The theoretical values of in situ stress and disturbed stress are obtained. The nonlinear mapping relationship of the boundary condition and the stresses at the measuring points is established by the evolutionary neural network. The measured in situ stress and disturbed stress in the unloading zone are imported into the neural network to obtain the boundary conditions. Finally, the boundary condition obtained by back analysis is assigned to the numerical model for calculating the stress field at the project site. The method proposed in this study was applied to analyze the stress field of Mengku Iron Mine in Xinjiang, China. It was found that the accuracy of back-analysis results has been greatly improved because the contributions of both the in situ stress and the disturbed stress were considered in the proposed method. Meanwhile, according to the engineering analysis, the maximum horizontal principal stress in the open-pit slope was reduced by a certain degree, with a maximum reduction of 30%–40% after mining. However, the major principal stress at 0–350 m below the mine pit increased remarkably, with an increment of above 60% compared to the in situ stress. It indicated that excavation unloading has a great influence on the local stress field.

Monitoring Analysis and Numerical Simulation of the Land Subsidence in Linear Engineering Areas

Non-uniform land subsidence can cause subgrade deformation and threaten the safety of linear projects such as high-speed railways. The Lunan high-speed railway is taken as the research background. Combined with the hydrogeological and engineering geological conditions, the regional land subsidence is analyzed by the combined method of the differential interferometric synthetic aperture radar (D-InSAR) and small baseline subset interferometric synthetic aperture radar (SBAS-InSAR), which is verified by using precise leveling and GPS monitoring data. The accurate land subsidence analysis of large-scale linear engineering is realized. The distribution situation and change laws of land subsidence in linear engineering areas are revealed. Then, a three-dimensional coupled numerical model of land subsidence along a large-scale linear project is established by using the finite difference method. The spatial distribution characteristics of land subsidence in the linear engineering area are quantitatively analyzed and predicted. The main factors affecting land subsidence and the degree of land subsidence are discussed while keeping the pumping rate constant. The results show that: 1) The combined method of D-InSAR and SBAS-InSAR has high accuracy in the land subsidence monitoring of linear engineering. 2) There are five non-uniform settlement funnels along the Lunan high-speed railway. The groundwater over-extraction and coal mining are the main reasons for the land subsidence. 3) Realizing water source conversion and reduce groundwater exploitation are the main factors in linear engineering areas as soon as possible.

DETERMINATION OF MAIN TECHNICAL PARAMETERS IN FORMING FOUNTAINS IN THE URBAN SPACES

The article deals with the problem of loss of the architects’ skills and knowledge to combine the parameters of urban spaces with effective models of fountains, which are aesthetically and economically sound, perform scenarios conditioned by the city-planning situation, where the basic concept is aimed at improving the space. Based on specialized publications in the field of water supply engineering systems, including publications on hydraulics and hydraulic engineering, the physical and chemical capabilities of water are considered from a comprehensive perspective as methods that allow its integrated use for absorption and transportation of the mechanical and dissolved impurities, cooling of air streams from the atmospheric air. The fountain is highlighted as an object of urban planning, and water and its movement as the main element that makes it possible to control the hydrophysical processes that take place in space and time, during the operation of buildings and are aimed at improving the space. Water movement is provided by the fountain engineering. The author underlines the factors that dictate the formation of engineering in the space: resources provision; topographic and engineering-geological conditions; climatic and acoustic characteristics. It is considered how the engineering of fountains during operation provides interaction of air and water streams. Described in detail: schemes of engineering systems of water supply and drainage of buildings; features of operation; calculation of the main elements that dictate the formation of structures in space. The main technical parameters in forming fountains in urban spaces have been identified - there is a tool that will help in creation of the effective models of fountains and sustainable development of spaces over time.

Analysis on Deformation and Stability of Tunnel Anchor Excavation under Broken Rock Mass

Based on the concrete engineering support of the tunnel anchor of the Dadu River Bridge on the Sichuan-Tibet Railway, the geological background of broken rock mass, extremely developed joints and fissures, and poor self-stability of surrounding rock within the range of side anchors in Chengdu, a three-dimensional elastoplastic numerical calculation method is used. The current engineering geological conditions and the tunnel anchor design plan are to establish a three-dimensional fine numerical simulation model of the Chengdu side tunnel anchor that comprehensively considers rock mass unloading, stratum classification, and anchor tunnel excavation and support structure. The “excavation-support” process in each construction footage is simulated to realize the three-dimensional calculation of the dynamic construction and support of anchor tunnels, and to study the surrounding rock deformation, stress and plastic zone distribution changes during the excavation process. Comprehensive analysis found that the deformation of surrounding rock during excavation shows that it develops toward the empty surface, and the displacement distribution is obviously affected by the distribution of ground stress and rock formation. The greater the buried depth, the greater the deformation of the surrounding rock.

Theoretical and Experimental Study on the Mechanism of Instability and Firing Gas in Hard Quartz Sandstone

The upper part of high gas coal seam often has a hard and thick sandstone roof, which provides the condition for the occurrence of gas accident in goaf caused by the friction effect for the sliding and instability of hard quartz sandstone. Based on the engineering background of the 1007 working face of Xiakuotan Coal Mine, the conditions of sliding instability of hard quartz sandstone and the possibility of the friction effect are discussed by combining theoretical analysis with the laboratory test. When the ratio of span to thickness is less than 2∼2.56, the hard-thick sandstone strata may slip and lose stability. The influence of friction velocity and gas concentration on the induced gas of quartz sandstone is analyzed and compared. The results show that the point spark, the spark beam, and the gas explosion time are inversely proportional to the relative friction velocity, and the intensity of the gas explosion is directly proportional to the gas concentration and the relative friction velocity. This paper provides the basis for the prevention and control of gas disasters in goaf and the control of hard and thick sandstone roof strata under similar engineering geological conditions. It is of great significance to promote the safe and efficient production of coal mines and to ensure the safety of personal and property.

Case study of pullout piles connected with cap

This research work presents experimental and numerical tests analysis of tension piles group with detailed investigations of engineering geological and geotechnical conditions. Experimental piles group pullout tests gave a new understanding about pile shaft bearing capacity, which was also simulated numerically with finite element method. The pullout test results are presented for pile group connected with pile cap.

Influence of Subgrade Splicing Mode and Width on Differential Settlement of Pavement Subgrade

In order to study the influence of subgrade splicing mode and width on differential settlement, the large-scale finite element analysis software ANSYS is used to establish the subgrade settlement model, in which the parameters are determined according to the actual subgrade width, widening mode and engineering geological conditions of the widening project of Anxin expressway. The influence of unilateral widening and bilateral widening on the settlement of widened subgrade, the maximum differential settlement on the top of widened subgrade and the influence on horizontal displacement of widened subgrade are systematically evaluated. The results show that for unilateral and bilateral widening, with the increase of widening width, the settlement of the middle line of the old road gradually increases, and the double side widening can make the weight of the widened embankment distribute to both sides of the old subgrade, which greatly improves the settlement coordination of the old and new Subgrade, and is beneficial to the stress of the pavement structure.

Experimental Study on Creep Characteristics of Saturated Sandy Soil with Different Fines Content

In order to better study and predict the post-construction settlement of sand with fine-grained blow-filled sand, sand samples with different fine-grained contents were prepared according to the actual engineering geological conditions, and one-dimensional creep tests were carried out to reveal the effect of fine-grained content on the creep characteristics of saturated sand. The results show that the creep curve of saturated sand has nonlinear characteristics and is basically divided into three stages: instantaneous deformation, rapid deformation and steady-state creep; When the content of fine grain is less than 25%, the strain is smaller than that of sand without fine grain, and the average strain is minimum when the content of fine grain is between 15%∼25%; When the content of fine grain is more than 25%, the strain of sand under the same load increases with the increase of fine grain content; The 5-element generalized Kelvin model can describe the creep characteristics of saturated sand with different fine grain content, the correlation coefficient of fitting curve is 0.964∼0.997, the creep parameters in the model are related to normal stress, and all the parameters increase with the increase of normal stress.

Application of Computer Three-dimensional Modeling in Engineering Engineering

With the development of science and technology and the development of our society, new technologies are continuously applied in our country’s engineering. Due to the complex geological phenomena such as faults, pinching, and outcrops in geological bodies, in order to express these phenomena when modeling 3D strata Regardless of whether it is a surface model, a volume model or a mixed model, there are problems of space division or surface intersecting. Due to the complexity of geological body topology, data errors and computer accuracy problems, these models often fail in the actual modeling process. Using level set theory can effectively solve this problem. Level sets use implicit functions to express surfaces, which can realize the expression of complex geological bodies and topological operations such as merge, intersection, and difference. In 3D geological modeling, after generating various geological interfaces by interpolation, these geological interfaces are expressed in level sets, and various complex topological operations are completed by level theory, and a 3D geological model expressed in level sets is established. On this basis, by inserting various engineering activity interfaces expressed by level set, and using level set theory to perform topological operations, geological models after various engineering activities can be constructed. Reuse algorithms to extract various geological interfaces or engineering activity interfaces, and construct stratigraphic models that can be used for real-time visualization or engineering evaluation (such as finite element calculation) or geological models after engineering activities. By establishing a three-dimensional geological model of the area where the construction project is located, architectural designers and construction personnel can analyze and study complex geological conditions, and provide technical support for engineering. By studying the three-dimensional geological model, this paper analyzes the engineering geological conditions and potential risks of the construction process in the study area, and proposes risk control measures, which can provide scientific decision-making basis for building design, construction, and risk prevention and control, and has a high promotion value. Experimental research results show that the application of computer three-dimensional modeling in engineering engineering can effectively reduce the cost of the project, ensure the quality and schedule, and greatly improve the construction efficiency of the project.

Investigation of Instability and Blasting Caving Technology of Composite Support Structure in the Goaf of Gypsum Mine

According to the structure form of room and pillar goaf in gypsum mine, the mechanical model of pillar roof composite supporting structure was established in this research. Based on the cusp catastrophe theory and energy dissipation theory, the energy dissipation relationship of the support structure was analyzed, and a new instability criterion of the support system was derived by introducing the control parameters α and β. On this basis, the study of blasting caving was carried out. The influence of row spacing and hole depth on blasting caving was analyzed using ANSYS/LS DYNA software. The blasting influence range, stress wave attenuation and vibration velocity attenuation indices are obtained, and the blasting parameters such as the optimal distance and depth of blast holes between pillars and roof were optimized. Based on the results of theoretical analysis and numerical, combined with the engineering geological conditions of Dahan gypsum mine, the practical study of blasting caving was carried out. The caving scheme and caving sequence was determined, then the blasting caving effect was analyzed. The caving effect was found to be good, and the applicability of the theoretical model is verified.

A DOFS-Based Approach to Calculate the Height of Water-Flowing Fractured Zone in Overlying Strata under Mining

The distributed optical fiber sensing (DOFS) is a technique that can obtain full spatial and temporal information concerning the behavior of a large range of measurand fields along a fiber path and realize the distributed monitoring of the overburden section under mining. To calculate the height of water-flowing fractured zone caused by the exploitation of coal, this study employed distributed optical fiber sensors with OSI-C-S optical frequency domain reflectometry (OFDR) technology and designed a similar-material model test based on the engineering geological conditions of Daliuta Coal Mine. Through the test, deformation characteristics of overlying strata were studied, the linear relationship was summarized between the strain gradient and the shear stress measured by fiber sensors when the rock layer cracks, and a method was proposed of using the measured strain to measure the height of the water-flowing fractured zone in overlying strata. The test results show that there are several locations where the sign of the shear stress changes (positive to negative or vice versa) in the overlying strata during the initial stage of coal seam mining. As the working face advanced, the change locations gradually concentrated at the place where the rock cracks. By identifying the breakpoints of the rock and the locations where the sign of the shear stress measured by fiber sensors changes, this paper calculated the height of the water-flowing fractured zone in Daliuta Coal Mine. After comparing the height with the abscission layer position in the model test and the predicted height by the empirical formulas in the specification, it has been found that the three results are basically consistent, which in turn verifies the accuracy of this method.

Sidorsky deposit of construction sands in the Volgograd region

Relevance of the research. Construction sands are the largest functional group of sands widely used in construction industry. This natural material is one of the most demanded for the production of manufactured products in the construction industry of the region. Purpose of the researchis to study the engineering-geological conditions of construction sands deposit for the production of the manufactured products of OAO Sebryakovsky plant of asbestos-cement products, as well as for construction organizations of the region. Research methods. Based on the analysis of extensive collection materials using laboratory and statistical methods, as well as the results of additional research, the physical-geographical, engineering-geological and technogenic conditions of the study area were examined. Results and their application. The useful stratum of the deposit is composed of Upper Quaternary alluvial sands, the average thickness of which is 8.6 m, penetrated thickness is up to 12.3 m. Overburden within the study area is represented by the soil-vegetation horizon – up to 0.2 m. The extracted raw materials are used in the production of mortars, which is confirmed by tests of a cement-sand grout, and as a filler in fine-grained concrete. The reserves of the deposit are calculated in categories A + B + C1 in the amount of 2313.2 thousand m3. The development of the deposit is recommended by the open method. Explored and recoverable reserves will ensure the operation of the enterprise with an annual demand of 100 thousand m3 per year for a period up to 2030. Conclusions. Based on the results of the studies, it should be noted that the Sidorsky deposit of construction sands is assessed as profitable and competitive in relation to the exploited deposits of sand in the Volgograd region.

Risk Assessment and Control Strategy of Residual Coal Pillar in Room Mining: Case Study in Ecologically Fragile Mining Areas, China

Gradual instability of coal pillars left behind underground with room mining is one of the main reasons for sudden roof caving in the gob, surface subsidence, and other significant hazards. Moreover, room mining implies great losses of coal resources. In this paper, the main failure mode and room mining coal pillar process were analyzed according to the coalfield regional engineering geological and hydrogeological conditions. A numerical model was adopted to study the effect of different sizes of coal mining pillars and progressive instability failure of coal pillar on the plastic zone’s evolution characteristics and stress field of coal pillars in the stope. The proposed technologies of cemented paste backfilling and reinforcement of residual coal pillars are applied, and a numerical simulation model is established to study the strata movement characteristics and analyze the stability degree of residual coal pillar and key aquiclude strata in the Pliocene series of Neogene. Consequently, the performance and application prospect were evaluated. The results obtained substantiate a new method for the long-term stability control of coal pillars in room mining and protecting the ecological environment in China’s western eco-environmental frangible area.

Improved design for accelerated consolidation of subgrade when building a highway on a weak base

This article deals with the design of the foundation of the subgrade of a motor road on a weak foundation (peat, sapropel) in difficult climatic and engineering-geological conditions. The features of physical and mechanical properties of soft soils imply the creation of non-typical design solutions using modern technologies and building materials. As a result, the theoretical studies of the processes of accelerated consolidation of weak soils were carried out and a design of the subgrade was proposed based on the use of electro-physical and filtration properties of various aggregates, namely the cathode layer (crushed stone from blast furnace coke or conductive coal), the drainage layer (sand) and the anode layer (crushed stone from dolomite limestone or basalt). The developed structure will allow reducing the consolidation time of a weak base and providing the necessary strength of the base by increasing shear resistance, which will increase the durability and reliability of the road, as well as reduce the technological construction time.

Geoecological justification of a project of sustainable shipping on a Volga channel section in the Nizhny Novgorod region

Background. The Volga river channel with rapids limiting the navigation parameters of large-tonnage vessels between the cities of Gorodets and Nizhniy Novgorod is considered in the structure of the Unified deep-water system of waterways of the European part of the Russian Federation.Aim. To justify the need to develop design solutions providing sustainable navigation in the limiting river section under study during the entire navigation period.Materials and methods. An analysis of engineering-geological and geoecological conditions of the region, including a limiting channel section of the Volga.Results. The engineering-geological and geoecological conditions of the region were characterized. A brief description of individual project proposals, including two priority construction projects, a low-pressure hydroelectric unit and a ship canal, was provided with a comparative assessment of natural and man-made factors arising during their implementation.Conclusion. The implementation of the project for the construction of the Volgo-Don 2 canal should be an important stage in the development of the Unified deep-water system of waterways in the European part of the Russian Federation. It will replenish the Don River from the Volga in order to improve navigation conditions, land irrigation, water supply to settlements, and power generation.

GEOTECHNICAL ANALYSIS OF TRANSFORMING A WATER MANAGEMENT STRUCTURE TO A TRANSPORTATION STRUCTURE

This paper analyzes the transformation of the culvert channel under the supply channel of the Gabcíkovo Waterworks into a road tunnel structure and the impact this had on the surrounding rock environment. It presents the engineering-geological conditions in the area, the current structuralmaterial characteristics of the culvert channel and its proposed transformation into a road tunnel. The results of the geotechnical analysis, realized through numeric modelling, are presented as a comparison of deformation changes in the rock environment with respect to changes in loading states corresponding with functional changes in the analyzed culvert.

The catastrophic landslide on the Black Sea coast which destroyed the Roman town of Bisonе (south of Kavarna town)

In the second half of the Ist century BC seismogenic landslide/rockfall tore off the front part of the Chirakman Cape in the western part of the Kavarna Bay. The rich quarters of the Roman city of Bisone slid down into the sea. According to data from underwater archaeology artifacts and walls of the settlement are found up to 80 m inside the sea. The paper considers the tectonic conditions, the geological-geomorphological structure of the landslide, the paleogeography of the coastal shelf during the Holocene and the hydrogeological and engineering geological conditions in the area. A reconstruction of the coastline and sea-level position during the catastrophic landslide has been developed. Stability analyses have been performed too.

The catastrophic landslide on the Black Sea coast which destroyed the Roman town of Bisonе (south of Kavarna town)

In the second half of the Ist century BC seismogenic landslide/rockfall tore off the front part of the Chirakman Cape in the western part of the Kavarna Bay. The rich quarters of the Roman city of Bisone slid down into the sea. According to data from underwater archaeology artifacts and walls of the settlement are found up to 80 m inside the sea. The paper considers the tectonic conditions, the geological-geomorphological structure of the landslide, the paleogeography of the coastal shelf during the Holocene and the hydrogeological and engineering geological conditions in the area. A reconstruction of the coastline and sea-level position during the catastrophic landslide has been developed. Stability analyses have been performed too.