scholarly journals Stabilization of Deep Roadways in Weak Rocks Using the System of Two-level Rock Bolts

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Tuan Minh TRAN ◽  
Ngoc Thai DO ◽  
Trung Thanh DANG ◽  
Duyen Phong NGUYEN ◽  
Trong Hung VO
Keyword(s):  
Rock Mass ◽  
Surrounding Rock ◽  
Rock Bolts ◽  
Weak Rocks ◽  
Total Displacement ◽  
Cable Bolts ◽  
Rock Mass Deformation ◽  
Technical Solutions ◽  
Primary Support ◽  
Mass Deformation

Large rock mass deformation around deep roadways in the weak rocks was a significantproblem in mining activities in Vietnam and other countries. The excavation of roadways leads to highreleasing stress, which exceeds the peak strength of spalling surrounding rock and causes it to enter thepost-failure stage. Tensile failures then initiate and develop around the roadways, which causes thefragmentation, dilation, and separation of surrounding rock. The capacity of the primary support systemis low, which results in a severe contraction in the whole section of roadways, which requires findingsolutions to prevent the deformation of rock mass around roadways and technical solutions fromstabilizing for deep roadways. To stability analysis of roadways can be applied analytical, experimental,semi-experimental, and numerical methods. This paper introduces the prevention mechanism of largedeformation of rock mass around roadways using 2-level rock bolts. The research results show that usingthe system of two-level rock bolts can reduce the values of tensile stress on the boundary of roadwaysrange from 10 to 15% compared with only one. The importance of the total displacement of rock mass onthe boundary of roadways will be reduced from 3.47 to 13.85% using six long cable bolts.

scholarly journals Stability Analysis of the Left Bank Slope of Baihetan Hydropower Station Based on the MF-DFA Method

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Haoyu Mao ◽  
Min Zhang ◽  
Biao Li ◽  
Nuwen Xu
Keyword(s):  
Rock Mass ◽  
Multifractal Spectrum ◽  
Surrounding Rock ◽  
Left Bank ◽  
Deformation And Failure ◽  
Bank Slope ◽  
Spectrum Width ◽  
Baihetan Hydropower Station ◽  
Rock Mass Deformation ◽  
Mass Deformation

Based on the left bank slope of Baihetan hydropower station in Southwestern China, a high-precision microseismic monitoring system was established. An early warning model of surrounding rock mass deformation and failure based on MF-DFA was proposed. The results showed that the multifractal characteristics of the microseismic and blasting waveform time series in the left bank slope were obvious, and the multifractal spectrum width of the blasting waveform is much larger than that of microseismic waveform. Before the slope cracks increased, the multifractal time-varying response characteristics of microseismic waveform showed strong regularity, which could be regarded as a precursor of surrounding rock mass deformation. Before the deformation and failure of surrounding rock mass, the multifractal spectrum width Δα showed an increasing trend while the multifractal spectrum of microseismic waveforms Δf(α) presented a decreasing trend, which can be regarded as a precursor of surrounding rock mass deformation; when deformation and failure occurred, Δα showed a decreasing trend and Δf(α) showed an increasing trend, which can be regarded as a deformation failure period; after the occurrence of deformation and failure, both Δα and Δf(α) showed a steady trend, and Δf(α) would approach to the zero line, which can be regarded as a stable period.

Slow rock mass deformation in the mountain side north of the Tungnakvíslarjökull outlet glacier in western part of the Mýrdalsjökull glacier

2020 ◽  
Author(s):  
Þorsteinn Sæmundsson ◽  
Páll Einarsson ◽  
Joaquin Belart ◽  
Ásta Rut Hjartardóttir ◽  
Eyjólfur Magnússon ◽  
...  
Keyword(s):  
Rock Mass ◽  
Slope Failure ◽  
Aerial Photographs ◽  
Outlet Glacier ◽  
Maximum Deformation ◽  
Total Displacement ◽  
Rock Mass Deformation ◽  
Mountain Side ◽  
Main Ideas ◽  
Mass Deformation

<p>A large slow rock mass deformation has been detected in a mountain side north of the Tungnakvíslarjökull outlet glacier, located in the western part of the Mýrdalsjökull glacier in Iceland. A group of scientist from the University of Iceland, National Land Survey and Icelandic GeoSurvey have worked on collecting data from several sources and installed monitoring equipment at the site. According to observations, which were based on comparison of DEM from aerial photographs from 1945 to 2019, the slope has been showing slow rock mass deformation since at least 1945. The rate of movements has been estimated for the period from 1945 to 2019. The data show that the total displacement since 1945 is around 200 m. The data also indicate that the deformation rate has not been constant over this time period and the data shows that the maximum deformation was between 1999 and 2004 of total of 94 m or about 19 m/year.</p><p>The mountain slope north of the Tungnakvíslarjökull outlet glaciers reaches up to around 1100 m height. The head scarp of the slide, which is almost vertical, is around 2 km wide rising from about 4-500 m in the western part up to the Mýrdalsjökull glacier at 1100 m in the east. The total sliding from the head scarp down to the present day ice margin is around 1 km<sup>2</sup>. The total volume of the moving mass is not known as the sliding plane is not known, but the minimum volume might be between 100 to 200 million m<sup>3</sup>. The entire slope shows signs of displacement and is heavily fractured and broken up. A GPS station that was installed in the uppermost part of the slope in August shows that the slope is moving about 3-9 mm per day, at a constant rate since installation.</p><p>There are two main ideas of the causes for this slow rock mass deformation. One is the consequences of slope steepening by glacial erosion, followed by unloading and de-buttressing due to glacial retreat. Another proposed cause for the deformation is related to its location on the western flank of the Katla volcano. Persistent seismic activity in this area for decades may be explained by a slowly rising cryptodome, which may also explain the slope failure.</p>

Deformation of underground excavations under conditions of the Gremyachinsk potassium salt deposit

2020 ◽  
pp. 113-124
Author(s):  
V. N. Toksarov ◽  
I. A. Morozov ◽  
N. L. Beltyukov ◽  
A. A. Udartsev
Keyword(s):  
Rock Mass ◽  
Geological Structure ◽  
Surrounding Rock ◽  
Key Factors ◽  
Underground Excavations ◽  
Deformation Control ◽  
Factors Influencing ◽  
Rock Mass Deformation ◽  
Mass Deformation ◽  
Roof Support

The analysis of rock mass deformation around permanent excavations in sylvinite seam at a depth of 1100 m is presented. Surrounding rock mass features occurrence of hard anhydrite-dolomite rocks in the roof and soft carnallite in the floor of underground excavations. The test openings were driven with height of 3.7 m and width of 6.0 m using a cutter- loader. The deformation control used 6 measurement points in the excavations with support by rockbolting in the patterns of 1.0×1.0, 1.5×1.5 and 2.0×2.0 m. Two measurement points were arranged in an unsupported excavation. It is found that the key factors influencing deformation of the perimeter of underground excavations are the rockbolting design and the geological structure of enclosing rock mass. For instance, the reinforcement of roof support decreases values and velocities of deformation both in the roof and sidewalls of excavations. The highest values of velocities of displacements are recorded in the floor. The increased displacements in the floor rocks should be expected when the distance between the excavation perimeter and the nearest interface of seams (layers) in the floor of a tunnel decreases. The presented results can be of use to experts in the fields of geomechanics as well as in design and construction of underground excavations.

Analysis on Factors Influencing Deformation of the Underground Cavities during the Construction Period

2012 ◽  
Vol 446-449 ◽  
pp. 2722-2726
Author(s):  
Chun Yu Gao ◽  
Jian Hui Deng ◽  
Fan Li Meng
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Hydropower Station ◽  
Construction Period ◽  
Underground Caverns ◽  
Underground Cavities ◽  
Rock Mass Deformation ◽  
Mass Deformation

The underground cavities of the Guandi Hydropower Station are Complex large-scale underground caverns. The quality of the surrounding rock masses of the underground cavities of the Guandi Hydropower Station is good and the deformation is normally less than 30mm. The structure surfaces have noticeable action for controlling the surrounding rock mass deformation. The time characteristic of the surrounding rock mass deformation is not noticeable.

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