Freeze-Thaw Effects on Stability of Open Pit Slope in High-Altitude and Cold Regions

The cycle of the freeze-thaw action must be taken into account in the stability analysis of an open pit slope in the high-altitude and cold regions, because the natural process of freeze-thaw poses a significant effect on mechanical properties of the rock mass. To achieve this purpose, a linear relationship between the geological strength index (GSI) and the Tianshan slope rock mass rating (TSMR) system is established considering the effect of the freeze-thaw action by introducing a freeze-thaw correction coefficient δ. The GSI value is modified for rock mass in high-altitude and cold regions. The improved Hoek-Brown criterion considers the influences of the freeze-thaw action and steep and gentle slopes. The research outcome is applied in the No. 4 minefield open pit coal mine in the Muli mining area. Numerical calculations are performed by inputting rock mass mechanical parameters obtained in traditional and modified criterions, to discuss the influences of the freeze-thaw action on the stabilities of both the present mining slope and the final slope at the end of the designed mining. The results show that the safety factors of the original slope are 2.33 and 1.67, respectively, while after the modification, they are 2.14 and 1.61, respectively. In terms of the No. 4 minefield open pit coal mine, the slope stability meets the design requirement, although taking the freeze-thaw cycle into account.

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Analysis of the Development of an Erosion Gully in an Open-Pit Coal Mine Dump During a Winter Freeze-Thaw Cycle by Using Low-Cost UAVs

Remote Sensing ◽

10.3390/rs11111356 ◽

2019 ◽

Vol 11 (11) ◽

pp. 1356 ◽

Cited By ~ 11

Author(s):

Chuangang Gong ◽

Shaogang Lei ◽

Zhengfu Bian ◽

Ying Liu ◽

Zhouai Zhang ◽

...

Keyword(s):

High Resolution ◽

Soil Erosion ◽

Coal Mine ◽

Development Process ◽

Open Pit ◽

Land Restoration ◽

Freeze Thaw ◽

Thaw Cycle ◽

Freeze Thaw Cycle ◽

Mine Dump

Open-pit coal mine dumps in semi-arid areas in northern China are affected by serious soil erosion problems. The conventional field investigation method cannot ensure a fine spatial analysis of gully erosion. With recent technological and algorithmic developments in high-resolution terrain measurement, Unmanned Aerial Vehicles (UAVs) and Structure from Motion (SfM) technology have become powerful tools to capture high-resolution terrain data. In this study, two UAV Photogrammetry surveys and modeling were performed at one opencast coal mine dump gully before and after a freeze-thaw cycle. Finally, a three-dimensional digital model of the slope of the drainage field was established, and a centimeter-level-resolution Digital Orthophoto Map (DOM) and a Digital Elevation Model (DEM) were created. Moreover, the development process of the erosion zone of the open-pit mine dump during a freeze-thaw cycle was studied by UAVs. The results show that there are clear soil erosion phenomena in the erosion gully of the dump during a freeze-thaw cycle. The erosion degree was different across regions, with the highest erosion occurring in high-slope areas at the upper edge of the bank. Moreover, the phenomenon of flake erosion and “crumble” was recorded. At the same time, the NE-E-SE slope and the high-sunshine radiation zone were seriously eroded. Finally, the relationship between the development process of the erosion gully and micro-topography factors was analyzed, providing managers with a sound scientific basis to implement land restoration.

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Substantiation of Safe Conditions During Undermining of Hydraulic Waste Disposal

E3S Web of Conferences ◽

10.1051/e3sconf/20184101007 ◽

2018 ◽

Vol 41 ◽

pp. 01007

Author(s):

Yuriy Kutepov ◽

Aleksandr Mironov ◽

Maksim Sablin ◽

Elena Borger

Keyword(s):

Rock Mass ◽

Waste Disposal ◽

Coal Mine ◽

Water Body ◽

Water Inflow ◽

Open Pit ◽

Coal Seams ◽

Geological Conditions ◽

Mine Workings ◽

Mine Dump

This article considers mining and geological conditions of the site “Blagodatny” of the mine named after A.D. Ruban located underneaththe old open pit coal mine and the hydraulic-mine dump. The potentially dangerous zones in the undermined rock mass have been identified based onthe conditions of formation of water inflow into mine workings. Safe depthof coal seams mining has been calculated depending on the type of water body – the hydraulic-mine dump.

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The Effects of Particle Gradation on Salinized Soil in Arid and Cold Regions

Water ◽

10.3390/w14020236 ◽

2022 ◽

Vol 14 (2) ◽

pp. 236

Author(s):

Xuebang Huang ◽

Zizhao Zhang ◽

Ruihua Hao ◽

Zezhou Guo

Keyword(s):

Particle Size ◽

Soil Samples ◽

Frost Heaving ◽

Particle Content ◽

Cold Regions ◽

Freeze Thaw ◽

Thaw Cycle ◽

Freeze Thaw Cycle ◽

Salinized Soil ◽

Size Grading

Particle size grading impacts salt-frost heaving and dissolution collapse events of salinized soil on northwestern China’s arid and cold region highways. However, the influencing mechanisms remain unclear and the impact of varying particle size grading needs further investigation. Hence, this study focused on these effects and the number of freeze–thaw cycles on the characteristic changes in highway salinized soil in arid and cold regions. Three soil columns with different gradations were prepared to explore the gradation and the number of freeze–thaw cycle affects on salinized soil’s salt-frost heaving and dissolution collapse characteristics. The multi-functional physical simulation platform conducted multiple freeze–thaw cyclic tests in the laboratory. Test results confirmed significant and conclusive effects of gradation and the number of freeze–thaw cycles on salinized soil’s salt-frost heaving and dissolution collapse behaviors. Poorly graded salinized soil with high coarse particle content caused repeated freeze and thaw engineering hazards, significantly affecting salinized soil’s displacement and deformation behaviors during freezing. Contrarily, an increased range of fine particles more easily involved the characteristics of salinized soil during thawing. Therefore, the fourth freeze–thaw cycle was a crucial time node. After four freeze–thaw cycles, the displacement and deformation of original salinized soil and B-grade salinized soil samples (poorly graded with high fine particle content) tended to be stable. In contrast, the displacement and deformation of A-grade salinized soil samples (poorly graded with high coarse particle content) increased the growth rate. The present research results contribute to in-depth knowledge of the effects of gradation and freeze–thaw cycles on the characteristics of salinized soil in northwestern China, providing excellent referenced data support for the prevention and control of highway salinized soil failures and other engineering projects in arid and cold regions of northwest China.

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Geomechanical and Acoustic Properties of Intact Granite Subjected to Freeze–Thaw Cycles during Water-Ice Phase Transformation in Beizhan’s Open Pit Mine Slope, Xinjiang, China

Water ◽

10.3390/w11112309 ◽

2019 ◽

Vol 11 (11) ◽

pp. 2309 ◽

Cited By ~ 5

Author(s):

Yu Wang ◽

Wenkai Feng ◽

Huajian Wang ◽

Jianqiang Han ◽

Changhong Li

Keyword(s):

Energy Balance ◽

Fatigue Damage ◽

Frequency Band ◽

Open Pit Mine ◽

Acoustic Properties ◽

Open Pit ◽

Cold Regions ◽

Detection Techniques ◽

Freeze Thaw ◽

Energy Balance Approach

The deterioration of rock geomechanical behaviors subjected to freeze–thaw (F–T) action is a determining factor for rock engineering and rock structures in cold regions. In this work, taking six groups of granite obtained from an open pit mine as the research object, F–T cycle treatment, in-situ AE (acoustic emission) monitoring and ultrasonic detection techniques were performed to experimentally reveal the effects of F–T fatigue damage on the mechanical and acoustic properties of granite. The results indicate that the F–T action impacts the rock’s mesoscopic structure, deformation, strength, P and S-wave velocities, AE pattern and energy release. The accumulated AE counts and accumulated AE energy show a decreasing trend as the F–T cycle increases. The frequency spectrum revealed that the width of the low frequency band decreases and the high frequency band increases with increasing F–T cycles, indicating that there is an increase in large-scale cracks for a sample with high F–T treatment. In addition, energy balance analysis further illustrates the energy dissipation and release mechanism. The energy proportion used to drive the crack propagation is relatively small with high F–T treatment, and the final released energy becomes the minimum. The energy evolution characteristics analyzed by the energy balance approach is in good agreement with AE results. It is suggested that the F–T fatigue damage influences the rock energy storage and release characteristics and the instability of rock in the cold regions.

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Characteristics of Unloading Creep of Tuffaceous Sandstone in East Tianshan Tunnel under Freeze-Thaw Cycles

Advances in Materials Science and Engineering ◽

10.1155/2019/7547564 ◽

2019 ◽

Vol 2019 ◽

pp. 1-16 ◽

Cited By ~ 3

Author(s):

Zhijun Zhou ◽

Haochen Zhan ◽

Jiangyang Hu ◽

Chenning Ren

Keyword(s):

Creep Rate ◽

Surrounding Rock ◽

Cold Regions ◽

Freeze Thaw ◽

Rock Samples ◽

Thaw Cycle ◽

Short Period ◽

Macro Scale ◽

Freeze Thaw Cycle ◽

East Tianshan

The physicomechanical properties of tunnel surrounding rock are influenced by many factors such as the external environment and freeze-thaw cycles, especially in engineering in high cold regions. To understand the characteristics of freeze-thaw cycles on the creep properties of rocks in high cold regions, a freeze-thaw test, SEM test, triaxial compression test, and triaxial unloading creep test were carried out for tuffaceous sandstone in the G575 East Tianshan Tunnel in Hami, Xinjiang. The results show the following: (1) the freeze-thaw cycle reduces the degree of cementation of mineral particles in a microcosm, manifested on a macro scale by the scaling mode and crack propagation mode; (2) the effect of freeze-thaw cycles reduces the compressive strength and shear strength of rock samples (i.e., ductility enhancement); (3) for tuffaceous sandstone, the unloading process and freeze-thaw cycle each lead to improved creep deformation in rock samples, and radial deformation is more sensitive to rock deformation and failure; and (4) the creep rate of surrounding rock can be reduced by confining pressure. The peak creep rate increased with freeze-thaw time, as did the overall creep rate. Attention should be paid to deformation within a short period, and necessary supporting and protection measures should be taken to reduce creep.

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Long-term Changes in the Surface Area in the Surroundings of the Open-cast Brown Coal Mine in Bełchatów (Poland)

10.5194/egusphere-egu2020-13862 ◽

2020 ◽

Author(s):

Natalia Bugajska ◽

Wojciech Milczarek ◽

Anna Kopeć ◽

Dariusz Głąbicki

Keyword(s):

Brown Coal ◽

Coal Mine ◽

Mining Area ◽

Research Area ◽

Open Pit ◽

Significant Activity ◽

Satellite Radar ◽

The Difference ◽

October 17 ◽

Open Cast

<p>Satellite radar interferometry, in particular time series techniques, allow to monitor the activity of the surface of vast areas, making them a complement and alternative to traditional geodetic methods, the use of which in such areas is often associated with significant restrictions. The above-mentioned areas definitely include open-cast mines, among others the analyzed Be&#322;chat&#243;w Brown Coal Mine (Poland).<br>During the studies, 216 satellite images acquired from the Sentinel-1A and Sentinel-1B satellites (path 175) for the period from October 17, 2014 to June 11, 2019 were used. Due to the fact that the research area was on two adjacent stages, it was necessary to combine data for the correct performance of the calculation process. The use of the SBInSAR imaging processing algorithm allowed to generate 839 interferograms carrying information about the difference in interferometric phases between pairs of images which satisfy the condition of the boundary size of the spatial and temporal base. As a consequence, it allowed to determine the displacements in the direction of the electromagnetic beam LOS (Line of Sight) that occurred in the mining area during this period.<br>Based on the carried out calculations, significant activity of the area around the open-pit mine was perceived. Dumping ground were analyzed - external Szczerc&#243;w Fields and internal Be&#322;chat&#243;w Fields, as well as excavations where mineral extraction is currently taking place. Continuous deformations (depressions and uplifts) associated with intensively conducted mining exploitation and complicated geological and mining conditions occurring in this area were observed (arrangement of rock layers, faults, the D&#281;bina salt debris separating the Be&#322;chat&#243;w Field from the Szczerc&#243;w Field).</p>

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Two-Dimensional Modeling of the Influence of Underground Mining Direction on Slope Stability in Coordinated Open-Pit and Underground Mining

10.21203/rs.3.rs-228554/v1 ◽

2021 ◽

Author(s):

Bowen Liu ◽

Zhenwei Wang ◽

Xinpin Ding ◽

Zhitao Wang ◽

Bin Li

Keyword(s):

Rock Mass ◽

Slope Stability ◽

Underground Mining ◽

Mining Area ◽

Two Dimensions ◽

Open Pit ◽

Engineering Practice ◽

Inverse Slope ◽

Coal Wall ◽

Mining Face

Abstract Under a background of coordinated open-pit and underground mining engineering practice in the Pingshuo mining area, a combination of numerical simulations and similar-model experiments was used to study the influence of the underground mining direction on slope deformation in two dimensions. The results show that the disturbance caused by inverse-slope mining is more obvious than that caused by along-slope mining. Underground mining presents an asymmetric influence on the open-pit slope; the slope rock mass on the open-off cut side is disturbed more than that on the coal-wall side. Compared with the slope in front of the advancing direction of the underground mining face, the degree of rock-mass damage and stress concentration of the slope of the open-off cut side are more serious. As such, in coordinated open-pit and underground mining practice, an along-slope mining direction is recommended to reduce adverse effects on slope stability and improve the recovery rate of coal resources.

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Determination of the Ultimate Underground Mining Depth considering the Effect of Granular Rock and the Range of Surface Caving

Mathematical Problems in Engineering ◽

10.1155/2021/5576786 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Rongxing He ◽

Jing Zhang ◽

Yang Liu ◽

Delin Song ◽

Fengyu Ren

Keyword(s):

Numerical Simulation ◽

Rock Mass ◽

Mechanical Model ◽

Surface Deformation ◽

Underground Mining ◽

Mining Area ◽

Open Pit ◽

Open Pit Mining ◽

Mining Depth

Continuous mining of metal deposits leads the overlying strata to move, deform, and collapse, which is particularly obvious when open-pit mining and underground mining are adjacent. Once the mining depth of the adjacent open-pit lags severely behind the underground, the ultimate underground mining depth needs to be studied before the surface deformation extends to the open-pit mining area. The numerical simulation and the mechanical model are applied to research the ultimate underground mining depth of the southeast mining area in the Gongchangling Iron mine. In the numerical simulation, the effect of granular rock is considered and the granular rock in the collapse pit is simplified as the degraded rock mass. The ultimate underground mining depth can be obtained by the values of the indicators of surface movement and deformation. In the mechanical model, the modified mechanical model for the progressive hanging wall caving is established based on Hoke’s conclusion, which considers the lateral pressure of the granular rock. Using the limiting equilibrium analysis, the relationship of the ultimate underground mining depth and the range of surface caving can be derived. The results show that the ultimate underground mining depth obtained by the numerical simulation is greater than the theoretical calculation of the modified mechanical model. The reason for this difference may be related to the assumption of the granular rock in the numerical simulation, which increases the resistance of granular rock to the deformation of rock mass. Therefore, the ultimate underground mining depth obtained by the theoretical calculation is suggested. Meanwhile, the surface displacement monitoring is implemented to verify the reasonability of the ultimate underground mining depth. Monitoring results show that the indicators of surface deformation are below the critical value of dangerous movement when the underground is mined to the ultimate mining depth. The practice proves that the determination of the ultimate underground mining depth in this work can ensure the safety of the open-pit and underground synergetic mining.

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Spatiotemporal Variation Characteristics of Groundwater Quality in A Semi-Arid Steppe Area in Northwest China

Nature Environment and Pollution Technology ◽

10.46488/nept.2021.v20i04.043 ◽

2021 ◽

Vol 20 (4) ◽

Author(s):

Quansheng Li ◽

Kai Zhang ◽

Yingming Yang ◽

Shan Chong ◽

Wenfeng Du ◽

...

Keyword(s):

Dissolved Oxygen ◽

Coal Mine ◽

Ph Value ◽

Groundwater Resources ◽

Vertical Direction ◽

Mining Area ◽

Open Pit ◽

Temporal And Spatial Distribution ◽

Pastoral Area ◽

Semi Arid

In this paper, the open-pit coal mine in semi-arid grassland was taken as the research object. The water samples of the open-pit coal mine and its surrounding areas were collected and the hydrochemical parameters were detected. The temporal and spatial distribution characteristics of the parameters such as pH, electrical conductivity, and dissolved oxygen in the groundwater were studied. The results showed that the groundwater in the study area was alkaline and brackish water. Climate factors might have a certain impact on the pH, conductivity, and dissolved oxygen of groundwater. The pH value of groundwater in the mining area was higher than that in the surrounding pastoral area, while the conductivity value of the mining area was between the pastoral area in the west and the Xilin river area in the east. The parameters of pH, conductivity and total dissolved solids of the four monitoring wells around the mining area showed a slow change or stable phenomenon in the vertical direction with the increase of groundwater depth. This study is of great significance to understand the characteristics of groundwater chemistry in mining areas and the rational development and utilization of groundwater resources.

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Numerical Simulation of Slope Stability Analysis of Open Pit Coal Mine Based on MIDAS/GTS

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.193 ◽

2012 ◽

Vol 256-259 ◽

pp. 193-197

Author(s):

Chong Xian Liu ◽

Yong Tao Gao

Keyword(s):

Slope Stability ◽

Coal Mine ◽

Mining Area ◽

Slope Instability ◽

Open Pit ◽

Shanxi Province ◽

North Slope ◽

Mining District ◽

The North

Based on mining area end slope stability evaluation engineer- ing of Pingshuo East open pit coal mine in Shanxi Province, ac- cording to the status quo of the North Slope of the first mining district of the East open pit coal mine as well as engineering g- eological investigation results, this article selected a represen- tative cross-section of the North Slope,adopted processing fu- nctions of finite element analysis software MIDAS/GTS, and re- spectively analyze slope stability under three conditions of the mining area of the initial excavation,backfilling and disposal,a- nd follow-up excavation.The paper concluded that Initial exca- vation caused slope instability; backfill slope is stable after di- sposal; follow-up excavation has essentially no effect on slope stability. The establishment and analysis are much closer to t- he real situation, objectively reflect the distribution of slope s- tability of the East open pit coal mine, and provide a design for open pit production safety.

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