Engineering Geological Characteristics Research Articles

К ВОПРОСУ ФОРМИРОВАНИЯ СВОЙСТВ ГИДРОТЕРМАЛЬНОМЕТАСОМАТИЧЕСКИХ ПОРОД КУРИЛО-КАМЧАТСКОЙ ВУЛКАНИЧЕСКОЙ ДУГИ

The article discusses the main regularities of the formation of engineering-geological features of hydrothermal-metasomatic rocks formed inside and on the surface of modern hydrothermal systems in areas of active volcanism due to the processing of the initial rocks of volcanic genesis by thermal waters. The conditions and successive stages of formation of various types of hydrothermal-metasomatic rocks and their corresponding trends in changing physical and mechanical properties are analyzed.

Procedures of engineering geological mapping applied to urban planning in a data-scarce area: Application in southern Brazil

Resultsfrom an engineering geological mapping study of the urban area of Ouro Preto in the state of Minas Gerais, Brazil, are presented. The goal of the study was to verify the efficacy of procedures, methods and classification schemes based on engineering geological mapping principles to generate data and maps for urban planning, restructuring (rehabilitation) and engineering projects. The study was developed at a 1:10,000 scale and based on field and laboratory studies and on the analysis and interpretation of aerial photography and satellite images. The selected study area has been urbanized for over 300 years and requires territorial planning and reorganization of land uses. The area is composed of highly variable rock types, unconsolidated materials and terrain features. Data collection and mapping were performed to identify and delineate 51 engineering geological units in terms of the spatial distribution of geological materials, genetic characteristics, mineralogy, the estimated strength, hydraulic conductivity interfaces and potential failure surfaces. All units were assessed in terms of excavatability conditions, predisposition to erosion and shallow translational landslide, suitability for sustainable urban drainage systems (SUDS), contaminant flow conditions, potential use as construction materials and foundation-related aspects. Recommendations for a detailed site investigation were made, and the suitability of geological materials for engineered fill was evaluated. A constraint zoning analysis was carried out to contextualize urban planning. The adopted procedures, methods and classification schemes were shown to be efficient when implemented in conjunction with intensive field studies and enabled the delineation of units with different engineering geological characteristics that are important for urban planning involving different users.

Engineering-geological characteristics of the sediments of the loess-palaeosol sequence of the key section Proniatyn (Podolian Upland)

The Proniatyn key section represents the loess-palaeosol sequence of the Upper and partially Middle Pleistocene of the Podolian Upland. A detailed description of the section is given, as well as the engineering-geological characteristics of the sediments of the loess-palaeosol sequence Proniatyn, which is quite well stratified. There are two horizons of the Upper Pleistocene loess and the upper horizon of the Middle Pleistocene loess have been clearly distinguished. The key section presents the Dubno (MIS 3) fossil soil, the Horokhiv fossil pedocomplex (MIS 5), as well as the well-developed deluvial-solifluction sediments over the Horokhiv pedocomplex, which contain a large number of redeposited Middle Palaeolithic artifacts. The engineering and geological features of sediments of the loess-palaeosol sequence Proniatyn have been studied in detail and compared with the characteristics of the corresponding horizons of the loess-palaeosol sequences of a number of sections of the Podolian and Volhynian Uplands. It is established, in particular, that in many aspects the loess-palaeosol sequence of Proniatyn key section is closer to the characteristics of sediments of the loess-palaeosol sequences of the Podolian Upland. The importance of studying the Proniatyn key section is enhanced by the fact that it is associated with the Middle Palaeolithic site, and in the structure of the Horokhiv fossil pedocomplex there are all sub-horizons of MIS 5. Furthermore, it contains a geophysical Blake event. Therefore, it is confirmed that the Proniatyn key section is an important stratigraphic benchmark of the Pleistocene of Podolian Upland. Key words: loess-palaeosol sequences, key section, Pleistocene, engineering-geological characteristics, solifluction, Palaeolithic.

Sandy Soils of Pre-Quaternary Continental Formations in the Territory of Russia

The engineering-geological features of the sands included in pre-Quaternary continental terrigenous formations (red and gray, coal-bearing and lignite-bearing, molasse and molasse coal-bearing), which are widespread in Russia, are characterized. The results of studying the composition, structure, condition, and properties of these soils within the various regions of Russia are presented.

Sandy soils of pre-Quaternary continental formations Russian territory

The engineering-geological features of the sands included in the pre-Quaternary continental terrigenous formations (red and gray-colored, coal-bearing and lignite-bearing, molasses and molasses coal-bearing), which are widespread in Russia, are characterized. The results of studying the composition, structure, condition and properties of these soils within the various regions of Russia are presented.

A novel mathematical model for predicting landslide displacement

Landslide displacement evolution is important for predicting landslide geological disasters. Because landslide displacement monitoring data are limited, in this paper we propose a novel model for predicting landslide displacement, namely the kernel grey model with fractional operators (FKGM). By combining the advantages of fractional modeling, kernel function methods and grey models, we derived the theoretical framework of FKGM. The parameters of FKGM were obtained using particle swarm optimization algorithm. Then, FKGM was applied in a case study of a landslide in Hubei, China. The engineering geological characteristics of the landslide were analyzed, and seven factors including rainfall and the rate of the reservoir water-level change were selected as inputs. The results show that the mean absolute percentage error and mean square error of FKGM are smaller than those of the least square support vector machine (LSSVM) and the classical grey prediction model—GM(1,1). The influence of the FKGM parameters was investigated. Our results indicate that FKGM can be applied to reliably predict large deformation of landslides.

Long-term behaviour and degradation of calcareous sand under cyclic loading

Calcareous sand has been used as the main filling material in numerous reef constructions. Therefore, understanding its long-term dynamic engineering geological characteristics under cyclic applications of traffic or wave loading is crucial to the design and prediction of the serviceability of reef infrastructures. Considering this, seven monotonic triaxial tests and 33 high-cycle (25,000 cycles) drained triaxial tests were conducted on calcareous sand with various mean effective stresses (p’) and cyclic stress ratios (ζ). The results show that the development of the accumulated axial strain (ε1acc) has a strong correlation with the positional relationship between the cyclic stress path and critical strength line (CSL) or static strength envelope (SSE) in the p’-q plane. The critical cyclic stress ratio ζc, that represents the cyclic stress path reaching the CSL, is proposed. When ζ>ζc, the growth rate of ε1acc with ζ increases drastically. Moreover, when the cyclic stress path approaches the SSE, ε1acc enters an incremental collapse state. The increase in p’ diminishes the dilatancy of the volumetric strain εv. However, this response of εv reverses from decreasing to increasing with increasing ζ. The resilient modulus (Mr) increases with the number of cycles (N) due to the initial densification. If εv dilation occurs, Mr will decrease with N as particles lose contact. A single parameter for the cyclic stress path ratio (ψ) considering the effects of p’, ζ, and SSE is proposed. Additionally, empirical formulas for calculating the ultimate ε1acc and Mr are established. Furthermore, particle degradation significantly worsens ε1acc and εv, but has a more profound effect on the compressibility of εv. This degradation is also detrimental to Mr. A certain deviation trend of the predicted values from the measured values is found to correspond with the relative particle breakage.

Characterization of a highly heterogeneous flysch deposit and excavation implications: case study from Auckland, New Zealand

Engineering geological characteristics of the rapidly growing Auckland urban area are of increasing interest due to ongoing and planned tunnels and excavations. Auckland is mainly underlain by Miocene-age East Coast Bays Formation (ECBF), a highly heterogeneous flysch deposit, and is also affected by lava flows from the Late Quaternary Auckland Volcanic Field (AVF). Therefore, excavations in the region can encounter highly variable rock mass. Here, the geological strength index (GSI) and rock mass rating (RMR) were applied to outcrop in coastal cliff exposures located on Auckland’s North Shore, to evaluate the engineering geological properties of the ECBF. Samples were also extracted for laboratory analysis of elastic wave velocities, intact strength parameters and thin section analysis of microtexture. Specific issues identified include lenses of the heavily zeolitized Parnell Volcaniclastic Conglomerate, and marked strength contrasts within the weaker ECBF siltstone and sandstone. The ECBF sandstone, where uncemented, is much weaker and is highly permeable, while the presence of smectite clay may be problematic for tunnelling if it disaggregates, forming a ‘sticky spoil’. The presence of larger-scale defects has been problematic for tunnelling, including the presence of low shear strength clay seams along ECBF bedding planes, and bedding planes intersecting tunnel crowns.

Effects of chemical composition on the solubility and geomechanical characteristics of gypsum rocks from Gachsaran Formation, Iran

Evaporite rocks of the Gachsaran Formation make the reservoirs and foundations of several important dam site in southwest Iran. The solubility of these rocks is the main cause of instability and leakage problems usually observed in these dam sites. Therefore, investigation and consideration of engineering geological characteristics of these rocks, including their solubility, is crucial. In the present study, 10 gypsum rocks of the Gachsaran Formation were selected from Masjed-Soleyman, Haftkel, and Ramhormoz areas in southwest Iran. The chemical and mineralogical compositions of the samples were determined through optical microscopy, XRD, and XRF analyses. Different characteristics of samples including physical and mechanical properties, solubility, and solution rate were determined. Then, the effects of the chemical composition of gypsum rocks on geomechanical characteristics, solubility, and solution rate were assessed. Results showed that the proportion of two main gypsum components of CaO and SO3 and the CaO/SO3 ratio has a significant effect on gypsum strength and solubility. Also, an increase in the abundance of minor oxides of Al2O3, Fe2O3, SiO2, and K2O leads to a decrease in the solution rate.

Fracturing technologies of deep shale gas horizontal wells in the Weirong Block, southern Sichuan Basin

Stimulation of hydraulic fracturing of horizontal shale gas wells in Weirong Block has always been facing many difficulties due to many factors such as complicated geological conditions, small differences between the horizontal principal stress and the vertical principal stress, high working pump pressures, and low sensitive sand ratios. In view of this, by combing the geological structure, engineering geological characteristics and the difficulties of fracturing of deep shale gas wells in Weirong Block, learning from the general idea of volumetric fracturing for shale gas reservoirs at home and abroad, we determined the main ideas and technical countermeasures for fracturing in the area and applied them to the subsequent fracturing practices of shale gas wells. And the following achievements were obtained. First, the conventional fracturing technology applied to the shale gas wells in Weirong Block resulted in low fracture complexity, small stimulated reservoir volume (SRV), difficulties in guaranteeing the effectiveness of perforation clusters, low strength of proppant adding, difficulties in obtaining higher conductivity, poor stable production capacity after stimulation, and difficulties in meeting the need of well fracturing with casing deformation. Second, in view of the difficulties of fracturing stimulation in deep shale gas wells of Weirong Block, super high pressure, huge displacement, large fluid volume, temporary plugging and diverting in fracturing, and variable displacement technology can effectively increase SRV and the complexity of fractures in distant wells. The effectiveness of multi-cluster perforation can be guaranteed by comprehensive utilization of multi-cluster perforation optimization technology, big displacement technology and temporary plugging and diverting & fracturing technology at slots. The continuous proppant-adding technology with huge displacement, high viscosity, low sand ratio, low density and small particle size can improve sand adding strength and fracture conductivity. Besides, the stimulation technology for casing deformed wells using coiled tubing fast processing + small diameter bridge plug and separate pumping technology of perforating gun have been formed. Third, after the above fracturing technologies have been applied in five shale gas horizontal wells in Weirong Block, the average absolute open flow (QAOF) reached 26.11 × 104 m3/d, indicating a good stimulation effect. In conclusion, this paper can provide meaningful reference for the development of deep shale gas wells of the similar type.

Engineering geological characteristics of Danube right bank between Kozloduy and Gorni Tsibar

The geotechnical properties of soils (clays of the Brusarci Formation and loess complex) spread over the area of Danube right bank between the town of Kozloduy and the village of Gorni Tsibar have been determined. Complex landslides and river erosion are the most important geodynamic processes in the study area. Engineering geological zoning has been carried out, with two separated zones. The second zone is characterized with most complicated geotechnical conditions due to distribution of both old landslides and recently landslide activation in some sub-zones.

Інженерно-геологічна характеристика порід лесово-ґрунтової серії опорного розрізу Лисогора (Подільська височина)

The Lysohora key section is one of the most complete and interesting sections of the loess-palaeosol sequence of the eastern part of Podolian Upland. This is the area where the Pleistocene loess-palaeosol sequence was deposited directly on the rocks of Precambrian crystalline shield, its weathered part (eluvium). The value of engineering-geological research of the section is increasing due to the fact that it is located near the city of Vinnytsia, which has been intensively built up in recent years. We emphasize that in this section Upper Pleistocene loesses play a minor role. The value of the Middle Pleistocene loesses, which are generally poorly studied, is abruptly growing. The Lysohora section was sampled. Above 30 monoliths were taken with the purpose of studying the engineering-geological characteristics of the sediments. Among them are grain size distribution, natural moisture content, plasticity index, soil density, porosity coefficient, subsidence, angle of internal friction, specific cohesion, deformation modulus, chemical composition of aqueous extract, humus content, CaCO3 content, etc. The results of the exploration of the loess-palaeosol sequence properties are correlated with the corresponding stratigraphic horizons of the other sections of Podolian Upland. Besides the main section, which was described in a pit, two additional cuts were studied: one on the Korshiv palaeosol complex, another one on the ice wedge pseudomorphosis of Yarmolyntsi palaeocryogenic stage. It is revealed that loess and palaeosol horizons are very different in their engineering-geological properties. In particular, insignificant subsidence is a characteristic of only individual samples from the upper horizon of the Middle Pleistocene loesses. Palaeosol horizons usually have higher values of density and natural humidity. They have a heavier particle size distribution. According to the analysis of the water extract, the highly soluble salts are practically washed away from the loess-palaeosol series. The significant influence of palaeocryogenesis processes on the formation of engineering-geological properties of rocks is also described. Key words: loess-palaeosol sequence, Pleistocene, engineering-geological characteristic of sediments, palaeocryogenesis.

Durability of water-affected paste backfill material and its clean use in coal mining

Backfilling, which is an example of the clean use of mineral resources, allows a safe work environment and provides a disposal means for mine tailings. Safe mining is significantly influenced by the durability of paste backfill material, which can be affected by water. In this study, the effect of water on the mechanical properties and permeability was experimentally examined with increasing curing time in the Taiping Coal Mine, China. The interaction of paste backfill material with water results in an exponential increase in the weakening coefficient with increasing curing time, and a linear decrease with higher water content. Slaking, a process in which cohesion is lost under the effects of water and physical disintegration, occurs in paste backfill material. Low hydraulic conductivity is found, which contributes to the durability of paste backfill material. Microscopic analysis shows that porous and nonuniform distributed structures account for the weak permeability and stable strength. On this basis, a durability classification chart for clean use is proposed; this classification scheme identifies three grades of durability affected by water. The engineering geological characteristics of each grade are provided, providing guidance for identifying the type and grading of durability of paste backfill material affected by water in coal mining. The approach was validated by successful application.

Research and Application of Comprehensive Survey Technology for Transmission Engineering in Shallow Sea Area

To carry out seabed engineering geological survey is one of the important technical measures to ensure the safety of submarine electric transmission lines. Firstly, the characteristics, principles and application scope of several kinds of geotechnical engineering survey techniques were analyzed. On this basis, a comprehensive survey technique for seabed engineering geology is proposed. By applying the comprehensive survey technology to the engineering geological survey of the submarine transmission line routing area in a certain sea area, the engineering geological characteristics of the area and the unfavorable geology and obstacles affecting the line safety are found out, which provides technical guidance for ensuring the transmission line safety. The rationality and applicability of the comprehensive survey technology are verified by practical examples, which can provide reference for other submarine geotechnical engineering survey and promote the development of marine survey technology in China.

Geological and geotechnical characteristics of N2 laterite in northwestern China

The Neogene Pliocene series (N2) laterite is a special zonal soil widely distributed in northwestern China. However, given that it is largely covered by loess and other Quaternary deposits, there has been a lack of in-depth studies on its engineering geological characteristics. In recent years, with the development of resources and the construction of grand-scale industrialization in northwest China, many projects (slope, tunnel, mining, etc.) have encountered geological engineering problems due to the N2 laterite. Investigating the engineering geological characteristics of the N2 laterite provides the key to solving these problems. Using N2 laterite samples from typical regions in northwestern China and conducting laboratory tests, this paper analyzes the mineralogical composition, particle size distribution, clay mineral content and microstructure characteristics of the N2 laterite. It discusses its origin and depositional environment characteristics, and probes into its physical, hydrological and mechanical properties. Finally, the engineering environmental effect of the N2 laterite is summarized. According to the results, the N2 laterite composition is dominated by quartz, followed by feldspar; interstitial materials mainly consist of fine grained-microcrystalline calcite and clay minerals; particle size distribution mainly covers clay and silt, with relatively uniform particle sizes; in clay minerals, the contents of hydrophilic minerals montmorillonite and illite/montmorillonite mixed layer are fairly high. N2 laterite is mainly an aeolian deposit, with medium water-holding capacity and plastic, hard-plastic or hard in its natural state, and as a medium swelling soil. It is relatively impermeable; under natural moisture content conditions, the N2 laterite has a relatively high strength, but, when subjected to long-term groundwater, its strength decreases rapidly. In addition, the N2 laterite is a medium-high compressibility soil.

Assessment of the engineering geological characteristics of the Bazoft dam site, SW Iran

The geotechnical parameters and permeability of the Bazoft dam site were investigated. The bedrock of the Bazoft dam site belongs to the Asmari and Jahrum (Eocene, Oligocene and Miocene) formations. Rock mass rating (RMR) and geological strength index (GSI) classification systems were used to evaluate the dam site. Physical, mechanical and dynamic tests were performed on samples in a rock mechanics laboratory. Shear strength parameters and geotechnical parameters of the rock mass were determined. The results of Lugeon tests for determining rock mass permeability were in the range of 10–30. Based on the RMR, the dam site is located in the ‘good’ category. Finally, the relationship between Lugeon, the number of joints and rock quality designation ( RQD) of the rock mass was evaluated using statistical analysis for 24 exploratory boreholes with a total length of 3400 m. The values of these parameters were determined and analysed using equations, tables and reports in sections of 5 m along the borehole. The results showed that the relationship between Lugeon with RQD and the joint number is an exponential equation with a good correlation coefficient. Multiple linear analysis also showed high accuracy of the estimated Lugeon based on RQD and joint number.

The failure mechanism and construction practice of large underground caverns in steeply dipping layered rock masses

The stability of large underground caverns in steeply dipping layered rock masses is not only affected by the engineering geological characteristics of surrounding rock masses, but also by the excavation sequences and reinforcement measures. Certain places around the periphery of underground openings, such as the high sidewalls, would exhibit significant displacement increases and various failure patterns if the excavation and support were not properly designed. These issues can, according to the basic principles of structurally-controlled concept, be largely attributed to the mechanical properties of bedding planes and other discontinuities. In order to clarify the possible mechanisms behind these failures and to realize the dynamic adjustment of construction, a thorough investigation was conducted to the underground caverns of the Wudongde hydropower station throughout the excavation process. The geological conditions and mechanical properties of the rock masses in the study area were first introduced in detail. Four examples were then presented following the overall logic from geological background to failure mechanism and finally to reinforcement practice. The first example focused on the local wedge-type instability analyses, including the collection of necessary information, the identification of potential blocks, as well as the determination strategies for the factors of safety. The second example illustrated typical tensile failure mode of steeply inclined strata induced by large-scale excavation. The sudden normal unloading of bedding planes led to observable fractures along these weaknesses and considerable increases in sidewall displacements. Large quantities of extra reinforcements had to be installed to control further development of fractured range of the upstream sidewall. The third example highlighted the long-range influence of excavations on the stability of downstream roof, where multistage displacement increase and shotcrete cracking took place as a result of stress concentration and strata buckling, possibly also of the local unfavorable discontinuities. The last example was related to the failure mode of combined discontinuities on the surfaces of piers between two pits. Lessons learned from these examples mainly involve what the mechanical behaviors of the steeply dipping layered rock masses in different places after excavation will be like, and to what extent these behaviors could be predicted or anticipated, which then put emphasis on the importance of geological investigations, and how the optimization of excavation sequence and bench height as well as the timely installation of regular supports could effectively reduce the risks of instability.

Inženjerskogeološke odlike terena opštine Gadžin Han

Engineering geological features of the terrain are one of the important factors for land use. Hence, engineering geological maps are the basis for good spatial and urban planning. Knowing location of unstable zones we can avoid major damage. Research carried out on the part of the municipality of Gadžin Han shows that it is endangered by landslides. The causes of landslides are numerous, mostly the lithology, degree of mechanical damage (cracking and weathering), morphology, hydrology and hydrogeology, vegetation etc. The most vulnerable part is Zaplanje area where the largest number of landslides is registered. This paper is overview of engineering geological features of municipality Gadžin Han with special review of landslides and falls.

EXPERIMENTAL STUDY ON PORE CHARACTERISTICS OF SALINE SOIL IN WESTERN JILIN PROVINCE

The microstructure of soil is the internal factor determining its engineering properties, especially the pore characteristics of soil. It is an important index reflecting the state and strength of soil. In order to further understand the engineering geological characteristics of the saline soil in Western Jilin Province, the pore characteristics and influencing factors of different depth saline soil in Nong'an area are studied by using the mercury intrusion method. The results show that:The porosity of the soil increases with the increase of depth, and the distribution of pores at different depths is different. According to the fractal theory, the distribution of pores has fractal characteristics, and the fractal dimension D of pores increases with the increase of depth. The pores of saline soil in the study area were divided into three grades:macropores(d30m),mesopores(7m d 30m), and small pores(d7m). The physicochemical properties of soil affect each other and decide their pore characteristics together, thus affecting their engineering geological properties. The results can provide a basis for exploring the strength mechanism of saline soil in Western Jilin Province.

The Application of Ecological Treatment Technology of Bolt and Lattice Beam in Highway Mountain Slope Support

In this paper, the ecological control technology of bolt and lattice beam is used to effectively control the slope of Highway Mountain. According to the engineering geological characteristics of the slope, the cause of the possible failure of the slope is analyzed. The code for design of building slopes is used to optimize the reasonable design parameters. The ecological treatment scheme of the shrubs planted in the bolt + lattice beam + sorghum trough is proposed. The scheme can effectively reduce the destruction of the masonry construction to the surrounding environment, reduce the erosion and infiltration of the slope surface, and effectively enhance the stability of the slope. The vegetation in the sorghum groove of the slope can be well coordinated with the surrounding vegetation. It is an effective plan for the new ecological control of the mountain slope, which can provide some reference for the reinforcement of the same kind of slope.