Engineering Geological Conditions Research Articles

Control of the Internal and External Staggered Distance of Coal Mining Face to the Water‐Conducting Fissures in the Overlying Strata of the Near Coal

In Northwest China, rainfall is low, water resources are scarce, and the ecological environment is fragile. For shallow‐buried and close‐spaced coal seams with a thickness of upper coal bed >60∼70 m, the water‐conducting fissures of the overlying rock will not penetrate the water‐isolating layer after the upper coal seam is mined; the internal and external gap angles of the water‐conducting fissures are not generated from the water‐isolating layer. We set out to explore the critical internal and external dislocations for the second significant development of water‐conducting fissures in the overlying rock after coal mining under control. A calculation model for the critical internal and external staggered distances of coal mining face in shallow‐buried and close‐spaced coal seams is established, the calculation formula is given, and the calculation formula for the critical seam mining ratio under the condition of internal staggered mining mode is given. Numerical simulation performed by UDEC methods: taking the overburden strata in the shallow‐buried and close‐spaced coal seam mining area of Shigetai Coal Mine as a prototype, it was verified that the critical internal and external offsets of the coal mining face in shallow‐buried and close‐spaced coal seams have a significant effect on the overlying water flow cracks in the mining of the lower coal seam. For the feasibility of developmental control, according to the engineering geological conditions of Shigetai, through the calculation method of external staggered distance, it is concluded that the distance of the open cut of the lower coal face and the upper coal face is only 21∼27 m, which is much smaller than the water barrier. It does not produce the critical distance of the water‐conducting cracks. Therefore, in the process of mining the lower coal seam, the water‐proof layer will produce water‐conducting cracks, lose its water‐proof performance, and cause water loss. This is also the cause of the water inrush accident in Shigetai Coal Mine.

Empirical analyses of excavation method and tunnel support system based on engineering geology of Tunnel No.8 at Jakarta – Bandung high-speed railway, West Bandung, Province of West Java, Indonesia

The Chinese Basic Quality (BQ) system was used to determine the rock mass classes and design tunnel support system of the Tunnel No.8 of the Jakarta-Bandung high-speed railway. As the BQ system is newly applied for tunnelling project in Indonesia and remains poorly understood, this research aims to determine rock mass classes at the tunnel construction site and propose the tunnel excavation method and support system alternative based on more widely used rock mass classifications of the Geological Strength Index (GSI) and Japan Society of Civil Engineers (JSCE) standard. Surface engineering geological mapping and evaluation of drill core samples were carried out to obtain accurate interpretation of subsurface engineering geological conditions, particularly the rock mass classes at the tunnel elevation. The results show that the tunnel construction area consists of very poor to fair classes of andesite breccia, tuff lapilli, and tuffaceous sandstone. The full-face method with auxiliary bench cut and multiple-bench cut method are to be applied at the tunnel sections consisting of rock mass classes CI and DII, respectively. The proposed tunnel support system is a combination of shotcrete, rock bolt, steel rib, and invert.

The Geological Characteristics and Its Mining Evaluation of Xincheng Gold Deposit in Jiaodong

Xincheng gold deposit is located in Xincheng Village of Jiaodong, Laizhou Jincheng, near Bohai Bay, and is one of the largest mines in China. The orebodies of Xincheng gold deposit located in Jiaojia fault zone are mainly located in the pyrite sericite-quartzized cataclasite belt and the pyrite-sericite-quartzized granodioritic cataclasite belt under the main fault plane (Fault Gouge). Based on the exploration data and test data, the occurrence characteristics of I and V major orebodies in the deposit are analyzed, and the mining evaluation is made on the basis of the hydrologic and environmental characteristics of the deposit. The results show that the rock of the Orebody, roof and floor is mainly massive igneous rock and Metamorphic Rock, which has high mechanical strength and is hard and semi-hard rock with simple engineering geological conditions The Ore and waste rock are not easy to decompose harmful substances, have no heat harm, the possibility of local surface deformation caused by mining is not big, the circulation of groundwater is bad, the evaporation is big, the water quality is bad, the mined-out area formed by mining has little influence on the stability of rock mass in the mining area. The main ore body in the study area is of good geological environment.

Dynamics of Engineering and Geological Conditions of Mineral Deposits (from Exploration to Exploitation)

The development of mineral deposits has strong transformative effect on the geological environment. At the same time, all the components of geotechnical conditions (relief, structure of rock massifs, hydrogeological and geocryological conditions etc.), formed over a long geological time, are actively changing. Geological processes are activated and new mining-geological processes are formed. New strata are formed on the Earth's surface along with the technogenic formations and technogenic deposits. Today, the scale of technogenesis in mining is comparable to the results of geological activities that have been going on for many millions of years. The reaction of the geological environment is immediate and is expressed in the development of large-scale engineering and geological processes, which often do not allow the further development of mineral resources and threaten the human life. Therefore, even at the early stages of prospecting and/or exploration, it is necessary to understand the dynamics of changes in surrounding medium in order to develop methods for proper managing of the ore extraction. By the example of a number of objects, all the stages of study of engineering-geological conditions are considered, the dynamics of their change, which led to the formation of engineering-geological processes affecting the further development of mineral resource, is estimated.

“Green” operation of a building - an object of cultural heritage

The aim of the study is to determine the further «green» operation of a building - an object of cultural heritage in technogenic conditions that formed in the 20-21 centuries, based on monitoring the actual engineering and geological conditions of the urban historical territory of Voronezh. The study of the engineering-geological conditions of the territory and the structures of the building was carried out in three stages. At the first stage, a reconnaissance survey was carried out to identify surface forms of manifestation of modern engineering and geological processes; at the second stage - examination and monitoring of soil properties of the foundations and the building structures; at the third stage - calculation of slope stability in the Midas GTS NX software package and selection of the optimal slope reinforcement with a retaining wall. Changes in the physical properties of soils and the violation of soil conditions on the slope of the historical territory of Voronezh during technogenic soaking of soils were revealed. Calculation of slope stability in the Midas GTS NX PC revealed the influence of the surrounding modern buildings on the deformation of the building structures -object of cultural heritage. The influence of technogenic changes in slope stability in the process of modern development on the urban historical territory on the «green» ecology, i.e. safe operation of the building - a cultural heritage site.

ВІБРОДИНАМІЧНИЙ МОНІТОРИНГ ГРУНТУ ТА КОНСТРУКЦІЙ ПРИ ВЛАШТУВАННІ ШПУНТОВОГО ОГОРОДЖЕННЯ КОТЛОВАНУ В УМОВАХ ЩІЛЬНОЇ МІСЬКОЇ ЗАБУДОВИ

In this work the problem is formulated and its urgency is substantiated. The plan of location of objects and engineering-geological conditions of the construction site are given. Structural solutions of sheet piling of the pit and protective screen and characteristics of the technical condition of adjacent buildings are presented. Vibrodynamic equipment for pile pressing is considered. The analysis and synthesis of scientific and technical sources and normative documents is carried out. The purpose of research is formulated. The results of vibrodynamic examinations and their analysis are presented. In particular, according to the program, records of vertical and horizontal accelerations of the soil and structures of adjacent buildings at the level of the foundation during various operations on the installation of bored piles. The figures show the time signals of horizontal and vertical accelerations and amplitude spectra. Data on vertical and horizontal accelerations of structures будів1 and building №2 and their comparison with admissible SWD norms are also given. It is noted that the made vibration protection screen in the soil of the foundation of the existing building allows to reduce horizontal vibration accelerations of the soil by 2-3 times, vertical 1.2-1.3 times. In particular, it was found that the adjacent buildings may be affected by vibrodynamic loads during the construction of a new building in a densely built-up city. The conclusions of researches are resulted and recommendations in which all technological process with observance of normative requirements of the device of bored piles under protection of casings for the purpose of minimization of vibrodynamic influence on existing buildings are formulated.

Geotechnical monitoring during construction in difficult soil conditions

One of the common and at the same time most difficult problems that developers may face is unstable soil layer at the base of a future building. This paper describes problems of construction on weak, subsidence and heaving soils in engineering and geological conditions of Kursk city. Real problem of construction property safety is shown with the example of one of the demanding geomorphological and lithological conditions of urban areas. The paper offers a description of geologic and hydrogeological features of the slope rock mass in the right bank of the Tuskar river. Groundwater level lies at 8.7 m. depth. It is possible to predict an increase in the level of groundwater in building maintenance because this area is potentially flooded. Various engineering and geological processes and such phenomena as ground subsidence, Karst, suffosia, landslides, flooding, etc., can also be found in the studied territory. Initially an insufficient engineering-geomorphological, hydrogeological, ecological and engineering-geological study of hazardous areas in the city of Kursk have led to its problematic development, which illustrates the situation with residential real estate in the studied territory. To predict dangerous engineering-geological processes and ensure the reliability of the construction fund, specific proposals have been developed for the organization of a geotechnical monitoring system based on the optimal integration of geomorphological, geodesic, engineering-geological, hydrogeological and environmental construction methods in complex engineering-geological conditions.

Study on the Mechanism of Gas Ignition by Friction Effect of Hard Quartz Sandstone Instability

When the upper part of a high gas coal seam has hard and thick sandstone roof, the gas explosion accident in goaf is even caused by roof collapse. Taking the mining of 1007 working face of 10 coal seam under Xia KuoTan Coal Mine as the engineering background, using the method of indoor experiment and theoretical analysis, the possibility of rock friction effect igniting gas is studied. Under the engineering geological conditions, the results show that the heat produced by the friction process of hard sandstone can ignite gas. According to the 3DEC numerical simulation, the instability characteristics of the overburden hard rock are studied. The results show that the size of the slab instability area is not changed when the length of the working face increases. When the thickness of the roof is increased, the area of sliding instability is increased and the degree of sliding instability is more intense. At the boundary of the tunnel, the overlying strata are subjected to the largest shear stress, and it tends to form a friction surface with greater slip instability.

Using the typification of mining-engineering facilities to substantiate deformation monitoring of opencast mining

To date, in the field of monitoring deformations of the earth’s surface in the area of opencast mining, there is almost no current regulatory and methodological documentation that regulates the conduct of observations and at the same time takes into account the features of existing mining facilities of opencast mining and the possibilities of modern survey technologies. The paper gives an approach to determining a set of methods for deformation monitoring within the territory of mining enterprises engaged in open-pit mining, based on the results of the typification of mining facilities. The developed typification makes it possible to estimate the degree of complexity of mining-engineering facilities, taking into account their size, features of engineering-geological, hydrogeological and orographic conditions, geodynamic processes. To increase the information content of mine surveying, as well as the quality and accuracy of deformation monitoring as a whole, it is proposed to include technologies for Earth remote sensing from space, namely, satellite-based synthetic aperture radar (SAR) interferometry, used within the proposed concept for areal monitoring of deformations and detection potentially hazardous areas at complex and particularly complex opencast mining facilities. The proposed approach to the organization of deformation monitoring was tested within the territory of the Khibiny apatite-nepheline deposit of the Rasvumchorr Plateau: the complexity of conditions for the development of the Tsentralny open pit was evaluated and recommendations were formulated for conducting mine surveying of deformations of the earth’s surface in its territory using satellite-based SAR interferometry. This method was used to analyze deformations of the earth’s surface for the periods from 2007 to 2011 and from 2015 to 2016 according to data from the ALOS PALSAR, TerraSAR-X and Sentinel-1 satellites.

Spatio-temporal evolution of stratigraphic-diffusive methane hydrate reservoirs since the Pliocene along Shenhu continental slope, northern South China sea

When biogenic methane produced in marine shallow sediments flows laterally into hydrate stable zones, there is likely to be formation of disperse stratigraphic-diffusive hydrate reservoirs that generally appear thin-bedded and disseminated. The stratigraphic-diffusive layers are also potential industrial exploitation targets because they have moderate abundance, wide distribution, and convenient mining maneuverability. After success of the second trial production in Shenhu area of South China Sea, it is urgent for us to find out the evolution dynamics of the stratigraphic-diffusive hydrate system which is widespread along oceanic continental slopes. Here, the Pearl River Mouth Basin in the northern slope area of South China Sea as a typical passive margin was selected to probe the principles of the accumulation mechanism and distribution pattern of stratigraphic-diffusive methane hydrates, determine the optimal degree of aggregation and spatial extension, and thus evaluate the potential recovery value. Based on the composite stratigraphic sequence, we theoretically described the occurrence characteristics of this type of stratigraphic-diffusive hydrate reservoirs. A two-dimensional model that coupled sedimentation process, fluid flow and reaction kinetics was designed to gauge the influence of engineering geological conditions and other controlling factors since the Pliocene (5.3 Ma) in this system. Several key parameters (including porosity, temperature, salt, and hydrate content) at three different moments, 5 Ma ago, 1.5 Ma ago and at present, were exhibited. The impacts of geothermal gradient and kinetic reaction coefficient on the evolution process were also discussed. Finally, the methane generated from local particulate organic carbons and different start time was used to verify the rationality of this theoretical approach. Our two-dimensional model clearly depicted the occurrence and accumulation characteristics of local stratigraphic-diffusive hydrates, disclosed the exploration value and exhibited the exploitation possibility.

IMPACT OF VARYING PROPERTIES OF GEOLOGICAL ENVIRONMENT ON THE FORMATION OF LOADS AT SHALLOW-LAYING UNDERGROUND STRUCTURES

Purpose. The purpose of this work is to consider the prospects for the use of jet grouting in urban development. On the example of the considered engineering-geological conditions to show the possibility of wide application of soil-cement elements. Methodology. To consider the main characteristic features of jet grouting, which prevail over traditional geotechnical technologies. To show the possibility of performing soil-cement elements not only in the conditions of strengthening the soil bases, but also in the conditions of anti-filtration elements when performing the protection of ditches. To present the ranges of strength characteristics of soil-cement material for soil conditions of Ukraine. Findings. The type and physical and mechanical properties of soils in which the jet-grouted element is performed will be one of the main factors influencing the geometric size of the elements and the strength of the soil-cement material. Originality. Collected and analyzed strength characteristics of soil-cement material and the presented ranges of their numerical values will allow to use them for future design of jet-routed elements in different soil conditions of Ukraine without the available personal developed practical base. Practical implications. In the progressive rhythm of urban development, the issue of new construction in the immediate vicinity of existing buildings, or the reconstruction of those in disrepair is acute. Due to its features and advantages, the technology of jet cementation allows to solve construction problems where other geotechnologies do not have the opportunity to be applied. Low dynamic impact will allow to perform soil-cement elements at strengthening of buildings and constructions in an emergency condition, low water permeability - to use jet elements as antifiltration, both single, and in joint work with other elements of designs of protection of ditches. Numerical experimental values of the strength of the material obtained by performing jet cementation, will predict the strength characteristics of future soil-cement elements.

ADVANTAGES OF NIEMFE METHOD IN GEOLOGICAL STATE MONITORING WHEN SOLVING APPLIED ENGINEERING PROBLEMS

Problem Statement and Purpose Finding effective methods for monitoring the state of engineering structures and geological conditions in their localization is an extreme­ly urgent issue today. The method of natural impulse electromagnetic field of the Earth (NIEMFE) is widely used for the solution of applied engineering-ecological, geological, geophysical and hydrogeological problems. The purpose of this work is to study the dynamics and the geological environment forecasting in conditions of increasing man-made load and prove the effectiveness of NIEMFE method in solving problems related to the violation of the engineering facilities operating conditions.Data & Methods Data from field observations conducted by employees of the De­partment of Geotechnogenic Safety and Geoinformatics of Ivano-Frankivsk National University of Oil and Gas were used to build the initial models. In particular, measure­ments by the NIEMFE method were performed on the territory of the school in the vil­lage Yunashkiv in the Rohatyn district and on the territory of the university building.Results The efficiency of using the NIEMFE method for solving geological engineer­ing problems is confirmed by the example of two diverse objects. The observations results obtained during the rocks stress-strain state study in the Yunashkiv village school in the Rogatyn district are considered. The NIEMFE method measurements allowed us to establish the stress-strain zones of the study area, which are related to the karst processes development. The analysis of the anomalies distribution and their intensities show that the territory is not stable and one should expect further karst manifestations and earth's surface and building deformation. The monitoring obser­vation results by the NIEMFE method are presented in order to track the dynamics of the change in the the IFNTUOG building state. The reason for the building damage, namely the design on the ancient river bed site, which led to the rocks strength loss due to the suffusion processes and the decomposition of the clay rocks underlying the foundation was identified. The influence of significant rainfall on the stress-strain state change of the studied territory was confirmed. It is proved that the NIEMFE method is a promising method for studying the rock mass stress-strain state in terms of determining the engineering structures stability and providing the deformation pro­cesses forecast.

Analysis of Land Subsidence Distribution and Influencing Factors in Yan'an New District Based on Time Series InSAR

Objectives The excavation and city in Yan'an New District is the largest geotechnical project in the collapsible loess gully region. Large-scale land creation, engineering construction and complex engineering geological conditions has caused a large number of uneven land subsidence, which is posing an increasing threat to the stability of urban infrastructure and public safety. Methods The ascending Sentinel-1A data stacks obtained during December 2017 to December 2018 were analyzed using the time series interferometric synthetic aperture radar (InSAR) technique, and the distribution characteristics of the post-construction land subsidence of the mountain excavation and city construction in Yan'an New District were obtained. The reliability of the detection results of InSAR technology was demonstrated by field investigation. Finally, based on the deformation monitoring results, the main influencing factors of land subsidence distribution were analyzed. Results (1) The results show that significant uneven land subsidence formed after the mountain excavation and city construction in Yan'an New District is mainly distributed in the filling area, and the maximum deformation rate reaches up to 120.1 mm/a. Field investigation validates the reliability and accuracy of the deformation results. (2)The remodeling of original loess and the change of its physical properties during the filling process is the main intrinsic factors of land subsidence in the filling area. Large-scale land creation determines the distribution of land subsidence, and the thickness of the filling are the main controlling factor of the distribution and size of land subsidence. In addition, human activities and changes in the geo-environment will also accelerate the development of land subsidence. Conclusions In order to achieve the early detection of potential geo-hazards and active risk prevention in the site selection and feasibility study stage of mega engineering projects in the Loess Plateau, the time-series InSAR technology can provide an effective technical that allows for the early detection of potential geo-hazards such as land subsidence and landslides, and provide a scientific basis for further monitoring and warning, planning and construction, geologic disaster prevention.

Sequence of studying engineering and geological conditions of mineral deposits from exploration to development

geological environment. Actively change all the components of engineering-geological conditions (EGC), formed during the long geological time: the topography, structure of rocks, hydrogeological and permafrost conditions, are formed by geological processes and, at the same time on the surface of the Earth formed a new strata of man-made structures, and often man-made deposits. The scale of technogenesis in mining today is comparable to the results of geological activity that took place over many millions of years. Therefore, even at the early stages of studying the EGC MD, it is necessary to understand the dynamics of changes in the EGC in order to provide preliminary protective measures. Purpose of work. Consideration of striking examples of the dynamics of the EGC MD (from exploration to development), in order to provide methods for managing these changes. Methodology. The article considers the stages of obtaining engineering and geological information for the period of MD operation, which will solve the problems of rational use of the subsoil and protection of the geological environment. Results. For example, the number of objects marked all the stages of learning to yoke the dynamics of their changes, which led to the formation of engineering-geological processes that adversely affect the further testing of MD. Summary. The reaction of the geological environment in the development of MD is not long in coming and is expressed in the development of large-scale engineering and geological processes, which often do not allow further development of MD and threaten people's lives. Therefore, even at the early stages of studying the EGC MD, it is necessary to understand the dynamics of changes in the EGC in order to provide preliminary protective measures.

The Bedrock and Earth Works of Compacted Powder Land in Coastal Areas

Wang, Q. and Chen, G., 2020. The bedrock and earth works of compacted powder land in coastal areas. In: Li, L. and Huang, X. (eds.), Sustainable Development in Coastal Regions: A Perspective of Environment, Economy, and Technology. Journal of Coastal Research, Special Issue No. 112, pp. 371-374. Coconut Creek (Florida), ISSN 0749-0208.The comprehensive evaluation of the site and foundation stability of geotechnical engineering investigation is an important basis for the design and construction of building foundations. Whether it is correct or not reflects the engineering geological conditions and the characteristics of geotechnical engineering, and is related to whether the engineering design and construction are safe and reliable. The measures are appropriate and the economy is reasonable. Aiming at the engineering practice of using compacted fill as the supporting layer of multi-layer civil building foundations in the construction of new rural areas in coastal areas, the engineering mechanics of compacted silt was studied through indoor and in-situ tests of compacted silt Characteristics, the basic physical and mechanical properties of silt as a filling material are analyzed, and the strength and deformation properties of compacted silt and undisturbed silt under different moisture contents are compared. The test results show that the compacted silt with good construction quality control It has better physical and mechanical properties under natural humidity, with higher strength and stiffness, and different moisture content has a greater impact on the strength and deformation characteristics of compacted silt than undisturbed silt, and should be strictly controlled during construction Water content of compacted silt.

Assessment of experimental friction parameters and contact property of pipe string for the estimation and verification of a solution for pipe stuck in the China's first rock pipe jacking

The first rock pipe jacking project of China in Chongqing Guanjingkou encountered a pipe sticking problem soon following the abrupt increase of jacking force. It was essential for the direct shear test results and stresses acting normal to the outer periphery of the pipe strings to be relevant in the understanding of jacking forces for the pipe stuck. In this paper, direct shear tests were performed on the frictional characteristic between a dolomite and concrete specimen using the same test method in the earlier companion paper. The normal stresses of the pipe string were obtained through plane strain finite element modeling of the pipe-jacking under different engineering geological conditions, contact characteristics, overburden and contact areas, the threshold values of the normal contact stresses increased dramatically have also been achieved, simultaneously. Then the jacking force needed for stuck pipe strings has been predicted based on the frictional test results and the normal stress simulation in order to determine where the temporary intermediate jacking stations (TIJSs) should be installed. Finally, the pipe stuck problem is solved successfully using the TIJS method, this result provides excellent reference data for the similar engineering problems in the future.

Characteristics of Roof Movement and Ground Pressure Behavior of Gob-side Entry Retaining by Roof Cutting in Continuous Mining

Gob-side entry retaining by roof cutting (GERRC) technology has been widely used in China, but application research of the entry-retaining technology in continuous mining is relatively scarce. Based on the analysis of the technology of continuous mining and GERRC, this study adopted the methods of theoretical analysis and in-field monitoring of ground pressure and behavior to obtain the roof movement characteristics and ground pressure distribution law during the entire process of roof directional pre-splitting, entry retaining, and entry reusing. Using the engineering geological conditions and analysis of field data of Dianping coal mine in Shanxi Province, the principal design parameters and technological process of GERRC in continuous mining were obtained. The structure model of the retained roadway roof in continuous mining was constructed to study roof movement patterns and the mechanism of stability control of the retained roadway. The movement regularity of the overlying strata in the mining and entry-retaining stage was obtained, enriching the theory of roof structure evolution and stress transfer under the condition of continuous mining with GERRC. The research results provide significant support for further popularization and application of the technology of GERRC.

Dynamic Response and Perturbation Design of Surrounding Rock in Blasting Construction of Small Radius Spiral Tunnel

To achieve a better blasting effect of ultra-long and deep buried spiral tunnel with a small radius, it is necessary to study the dynamic response and disturbance of blasting construction. As the engineering background with a poor engineering geological condition, this paper uses the Midi spiral-tunnel in Yunnan province that has a small radius of curvature, a large burial depth, and a large excavation distance. The blasting load is determined first by calculation. Under different blasting construction parameters, the deformation and dynamic vibration responses of the surrounding rocks are studied using the finite element numerical method. The damage mechanism of rock under the blasting load is analyzed. The tunnel engineering blasting is designed and calculated, and the small distance disturbance design of spiral tunnel blasting construction with a small radius is performed from the excavation method and blasting parameters. The results serve as a reference to reveal the surrounding rock dynamics in blasting construction of the spiral tunnel with a small radius.

Numerical simulation study of the support system by gob-side entry retaining by roof cutting

Gob-side entry retaining by roof cutting (GERRC) is an innovative, long-wall mining method that has been widely used in China as a new mining revolution. However, current research on the influence of this technology on the support system remains limited. To understand the response of each supporting structure after cutting the roof, this study uses the cable element and beam element built in the finite difference software FLAC3D to simulate the bolt, anchor cable, steel beam, and single hydraulic props based on the engineering geological conditions of the Lvtang Coal Mine in Guizhou Province, China. Then, the force and displacement changes of each supporting structure between the GERRC and traditional coal pillar mining are compared and analyzed. Simulation results reveal that during the process of conventional mining, the force and deformation of anchor cable behind the working face is relatively large; furthermore, even yield and breaking of the cable occurs. Meanwhile, the serious deformation of a single hydraulic prop occurs, which affects the normal use of the roadway. When the GERRC is adopted, the force of each supporting structure is reduced by 17.6% on average and the deformation is not obvious. Moreover, using the GERRC decreases the stress of the supporting and reduces the displacement of solid coal in the roadway by 33.3%. Finally, the concentration degree of stress becomes lower, and the environment of retaining roadway is more optimized.

Tunneling-induced deep-seated landslides: a case study in Gulin County, Sichuan, China

The excavation of a highway tunnel revived an ancient landslide in Gulin County, Sichuan Province, China, which resulted in many severe problems such as ground surface cracks, tunnel deformation, and supporting structure damage. This paper focused on the interaction between the old landslide and the tunnel. First, the engineering geological conditions and deformation characteristics of the ancient landslide were determined on the base of field geological survey and geological prospecting. Second, the calculation parameters of the sliding body and sliding zone were obtained by back analysis to the surface deformation monitoring data. Finally, the failure mechanism of landslide due to tunnel excavation was discussed by three-dimensional numerical simulation, and the effect of proposed reinforcement measures was evaluated. The investigation results show that the ancient landslide consists mainly of gravel and block stones, and the major reason for the landslide failure is that the tunnel is exactly across the ancient landslide belt. The sliding surface below the left tunnel is gentle, and the thick sliding body prevents the upper body from sliding largely. Therefore, the deformation of the sliding body mainly occurred in the region above the tunnel. The calculated overall deformation range and value for the sliding body by back analysis are in good agreement with the field survey results and slope deformation monitoring data. According to the tunnel construction period and deformation characteristics of the sliding body, it is suggested to remove some part of the sliding body above the tunnel. The numerical simulation results show that, after removal, the sliding body and tunnel are small in deformation and are stable. The research results in this paper not only keep the tunnel under good construction and operation but also ensure the people and their property, which saves much construction cost and provide a valuable reference to similar projects.