Analyze of the Affection of Excavation Unloading of the Rock Mass of the Spillway Tunnel of a Hydropower Station on the Slope’s Stability

2012 ◽  
Vol 594-597 ◽  
pp. 621-626 ◽  
Author(s):  
Le Hua Wang ◽  
Jun Lei Bai
Keyword(s):  
Rock Mass ◽  
Hydropower Station ◽  
Engineering Practice ◽  
Tunnel Face ◽  
Tunnel Excavation ◽  
Slope Rock ◽  
Spillway Tunnel ◽  
The Stability ◽  
Unloading Effect

After the excavation of the rock , the rock mass stress state changes and the quality of rock mass damage deterioration. Rock excavation of spillway tunnel of the hydropower station may have some influence on the stability of the tunnel-face side slope. In this paper, combined with the engineering practice, based on the unloading rock mass theory and through two dimensional finite-difference method. Selected seven feature points near the excavation surface as monitoring points for calculation ,then calculated the effect on the stress and strain of the slope caused by the excavation of the spillway tunnel and analysed the changes in the distribution of the slope rock mass plastic zone and the point factor of safety. The results show that spillway tunnel excavation in excavated slope have some impact on the excavated slope stability, and it is more obvious for the effect on stability of excavated slope in considering rock mass unloading effect than do not consider the rock mass unloading effect.

Application of ABAQUS in Surrounding Rock Stability Analysis of Shallow Large Cross-Section Tunnel

2015 ◽  
Vol 777 ◽  
pp. 8-12 ◽  
Author(s):  
Lin Zhen Cai ◽  
Cheng Liang Zhang
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Strong Support ◽  
Surrounding Rock ◽  
Tunnel Engineering ◽  
Tunnel Excavation ◽  
Rock Stability ◽  
Rock Bolting ◽  
Excavation Support ◽  
The Stability

HuJiaDi tunnel construction of Dai Gong highway is troublesome, the surrounding-rock mass give priority to full to strong weathering basalt, surrounding rock integrity is poor, weak self-stability of surrounding rock, and tunnel is prone to collapse. In order to reduce disturbance, taking advantage of the ability of rock mass, excavation adopt the method of "more steps, short footage and strong support". The excavation method using three steps excavation, The excavation footage is about 1.2 ~ 1.5 m; The surrounding rock bolting system still produce a large deformation after completion of the first support construction, it shows that the adopted support intensity cannot guarantee the stability of the tunnel engineering. Using ABAQUS to simulate tunnel excavation support, optimizing the support parameters of the tunnel, conducting comparative analysis with Monitoring and Measuring and numerical simulation results, it shows that the displacement - time curves have a certain consistency in numerical simulation of ABAQUS and Monitoring and Measuring.

scholarly journals Variable Weight Matter–Element Extension Model for the Stability Classification of Slope Rock Mass

Mathematics ◽  
2021 ◽  
Vol 9 (21) ◽  
pp. 2807
Author(s):  
Shan Yang ◽  
Zitong Xu ◽  
Kaijun Su
Keyword(s):  
Rock Mass ◽  
Classification Criteria ◽  
Evaluation Index ◽  
Open Pit ◽  
Constant Weight ◽  
Extension Model ◽  
Variable Weight ◽  
Slope Rock ◽  
The Stability ◽  
Index Value

The slope stability in an open-pit mine is closely related to the production safety and economic benefit of the mine. As a result of the increase in the number and scale of mine slopes, slope instability is frequently encountered in mines. Therefore, it is of scientific and social significance to strengthen the study of the stability of the slope rock mass. To accurately classify the stability of the slope rock mass in an open-pit mine, a new stability evaluation model of the slope rock mass was established based on variable weight and matter–element extension theory. First, based on the main evaluation indexes of geology, the environment, and engineering, the stability evaluation index system of the slope rock mass was constructed using the corresponding classification criteria of the evaluation index. Second, the constant weight of the evaluation index value was calculated using extremum entropy theory, and variable weight theory was used to optimize the constant weight to obtain the variable weight of the evaluation index value. Based on matter–element extension theory, the comprehensive correlation between the upper and lower limit indexes in the classification criteria and each classification was calculated, in addition to the comprehensive correlation between the rock mass indexes and the stability grade of each slope. Finally, the grade variable method was used to calculate the grade variable interval corresponding to the classification criteria of the evaluation index and the grade variable value of each slope rock mass, so as to determine the stability grade of the slope rock. The comparison results showed that the classification results of the proposed model are in line with engineering practice, and more accurate than those of the hierarchical-extension model and the multi-level unascertained measure-set pair analysis model.

scholarly journals The Influence of Different Assist Gases on Ductile Cast Iron Cutting by CO2 Laser

2017 ◽  
Vol 17 (4) ◽  
pp. 109-114 ◽  
Author(s):  
J. Meško ◽  
R. Nigrovič ◽  
A. Zrak
Keyword(s):  
Cast Iron ◽  
Laser Cutting ◽  
Roughness Parameter ◽  
Cutting Speed ◽  
Nodular Cast Iron ◽  
Ductile Cast Iron ◽  
Engineering Practice ◽  
Technological Parameters ◽  
The Stability

Abstract This article deals with the technology and principles of the laser cutting of ductile cast iron. The properties of the CO2 laser beam, input parameters of the laser cutting, assist gases, the interaction of cut material and the stability of cutting process are described. The commonly used material (nodular cast iron - share of about 25% of all castings on the market) and the method of the laser cutting of that material, including the technological parameters that influence the cutting edge, are characterized. Next, the application and use of this method in mechanical engineering practice is described, focusing on fixing and renovation of mechanical components such as removing the inflow gate from castings with the desired quality of the cut, without the further using of the chip machining technology. Experimental samples from the nodular cast iron were created by using different technological parameters of laser cutting. The heat affected zone (HAZ), its width, microstructure and roughness parameter Pt was monitored on the experimental samples (of thickness t = 13 mm). The technological parameters that were varied during the experiments included the type of assist gases (N2 and O2), to be more specific the ratio of gases, and the cutting speed, which ranged from 1.6 m/min to 0.32 m/min. Both parameters were changed until the desired properties were achieved.

scholarly journals Numerical Analysis of Slope Stability Due to Excavation of Diversion Tunnel at Pamukkulu Dam Site, Indonesia

2021 ◽  
Vol 6 (2) ◽  
pp. 102
Author(s):  
Wakhid Khoiron Nugroho ◽  
I Gde Budi Indrawan, Dr. ◽  
Nugroho Imam Setiawan
Keyword(s):  
Slope Stability ◽  
Outlet Section ◽  
Inlet Section ◽  
Residual Soil ◽  
Basalt Lava ◽  
Tunnel Excavation ◽  
Earthquake Load ◽  
The Stability ◽  
Model Strength

Located in the Takalar Regency of South Sulawesi Province, the Pamukkulu Dam is planned to use a tunnel type as its diversion structure. One of the critical parts in the tunnel construction is the stability of portal slopes. This research aimed to estimate the effect of tunnel excavation on the stability of the portal inlet and outlet slopes under static and earthquake loads by using the finite element method. The slope stability analyses were carried out under conditions of prior to and after tunnel excavation. The input parameters used were laboratory test results in the forms of index properties and mechanical properties taken from rock core drilling samples, completed with the rock mass quality parameters based on the Geological Strength Index (GSI) classification. The Mohr-Coulomb failure criterion was used to model strength of the soil, while the Generalized Hoek-Brown failure criterion was used to model strength of the rocks. The results of rock cores analysis using the GSI method showed that the inlet tunnel slope consisted of four types of materials, namely residual soil, fair quality of basalt lava, good quality of basalt lava, and very good quality of basalt lava. Meanwhile, the outlet portal slope consisted of three types of materials, namely residual soil, good quality basalt lava, and very good quality basalt lava. The calculated horizontal seismic coefficient for the pseudo-static slope stability analysis was 0.0375. The analysis results of slope stability in the Y1 inlet section had a critical Strength Reduction Factor (SRF) value of 2.35 in a condition prior to the tunnel excavation and a critical SRF value of 2.34 after the tunnel excavation. The Y2 outlet section had a critical SRF value of 13.27 in a condition before tunnel excavation and a critical SRF value of 5.55 after the tunnel excavation. The earthquake load addition at the Y1 inlet section showed a critical SRF value of 2.05, both before and after the tunnel excavation. The Y2 outlet section showed a critical SRF value of 11.49 before the tunnel excavation and a critical SRF value of 5.54 after the tunnel excavation. The numerical analysis results showed that earthquake load reduced critical SRF values of the slopes. At the Y1 inlet section, the tunnel excavation did not have a significant effect on slope stability. It was demonstrated by an extremely small decrease in a critical SRF value of 0.43% for a condition without an earthquake load and an unchanged critical SRF in a condition with an earthquake load. At the Y2 outlet section, the tunnel excavation had a more significant effect on the slope stability. It was exhibited by the decrease in the critical SRF value of 58.18% in a condition without an earthquake load and a decrease in the critical SRF value of 51.78% in a condition with an addition of an earthquake load. However, the analysis of slope stability for both sections showed that all design slopes were above the required allowable safety factor value.

scholarly journals Stability Assessment of the Excavated Rock Slope at the Dagangshan Hydropower Station in China Based on Microseismic Monitoring

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
K. Ma ◽  
N. W. Xu ◽  
Z. Z. Liang
Keyword(s):  
Rock Mass ◽  
Slope Stability ◽  
Monitoring System ◽  
Rock Slope ◽  
Rock Slope Stability ◽  
Hydropower Station ◽  
Bank Slope ◽  
The Stability ◽  
The Right ◽  
Dagangshan Hydropower Station

A high-resolution microseismic (MS) monitoring system was implemented at the right bank slope of the Dagangshan hydropower station in May 2010 to analyse the slope stability subjected to continuous excavation. The MS monitoring system could real-time capture a large number of seismic events occurring inside the rock slope. The identification and delineation of rock mass damage subject to excavation and consolidation grouting can be conducted based on the analysis of tempospatial distribution of MS events. However, how to qualitatively evaluate the stability of the rock slope by utilizing these MS data remains challenging. A damage model based on MS data was proposed to analyse the rock mass damage, and a 3D finite element method model of the rock slope was also established. The deteriorated mechanical parameters of rock mass were determined according to the model elements considering the effect of MS damage. With this method, we can explore the effect of MS activities, which are caused by rock mass damage subjected to excavation and strength degradation to the dynamic instability of the slope. When the MS damage effect was taken into account, the safety factor of the rock slope was reduced by 0.18 compared to the original rock slope model without considering the effect. The simulated results show that MS activities, which are subjected to excavation unloading, have only a limited effect on the stability of the right bank slope. The proposed method is proven to be a better approach for the dynamical assessment of rock slope stability and will provide valuable references for other similar rock slopes.

Stability Analysis of Dangerous Rocks on the Slope of a Hydropower Station

2013 ◽  
Vol 405-408 ◽  
pp. 621-629 ◽  
Author(s):  
Hai Feng Li ◽  
Guo Xing Zhang ◽  
Tao Huang ◽  
Qiu Jing Zhou
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Discontinuous Deformation Analysis ◽  
Hydropower Station ◽  
Deformation Analysis ◽  
Time Interval ◽  
Block Method ◽  
Fractured Rock Mass ◽  
Unstable Failure ◽  
The Stability

Dangerous rocks are among the most significant factors in analyzing the stability of high slopes, and are the main geological hazards on such slopes. These rocks are typical spatial blocks. The unstable failure of dangerous rocks poses evident spatial features. Consequently, their stability should be calculated by considering it as a three-dimensional (3-D) problem. In this research, the general block method of fractured rock mass and 3-D discontinuous deformation analysis (DDA) are used to study the stability of dangerous rocks on the slope of a hydropower station. The general block method of fractured rock mass is used to generate dangerous rocks and to assess the geometric mobility of blocks. The progressive unstable failure of dangerous rocks is also analyzed. Moreover, 3-D DDA is implemented to examine the stability of dangerous rocks, including the regularity of their unstable failure. The failure sequence of each batch of blocks estimated by general block theory is the same as that in the results of 3-D DDA. The decrease in the shear parameters of the structural plane shortens the time interval of failures, but increases the number and capacity of blocks.

Study about Mechanic Parameter of Slope Rock Mass' Structure Plane

2013 ◽  
Vol 368-370 ◽  
pp. 1551-1555
Author(s):  
Si Yu Wu ◽  
Bo Huang ◽  
Rui Jun Liu
Keyword(s):  
Rock Mass ◽  
Deformation Modulus ◽  
Friction Angle ◽  
Mechanical Parameters ◽  
Test Results ◽  
Rock Mass Structure ◽  
Stability Of Slope ◽  
Slope Rock ◽  
The Stability ◽  
Structure Plane

Firstly, the stability of the slope need to determine mechanical parameters of slope rock mass such as deformation modulus, Poissons ratio, cohesion and internal friction angle, etc. For intact rocks, the mechanical parameters mentioned before are easy to determined. While the stability of slope rock mass is controlled by the deformation and intensity. Therefore, how to determine the mechanical parameters of the structure is the key to analyze the stability of slope rock mass. This paper intends to set the slope rock mass below some extra-large bridge as the research object and use numerical calculation to determine the mechanics parameters of rock mass structure plane on the basis of rock sample mechanics test results.

THE INFLUENCE OF CLASSIFICATION PARAMETERS UNCERTAINTY ON ROCK MASS QUALITY ASSESSMENT

2020 ◽  
Author(s):  
Ahmed Mušija ◽  
Kenan Mandžić
Keyword(s):  
Rock Mass ◽  
Uniaxial Compression ◽  
Compression Strength ◽  
Working Environment ◽  
Uniaxial Compression Strength ◽  
Adequate Model ◽  
Geotechnical Characteristics ◽  
Road Tunnels ◽  
The Stability

The construction of underground objects is a very complex task that takes into account a large number of input parameters that affect the process of building and stability of underground objects during the exploatation. Engineering geological and geotechnical characteristics of the rock mass represent the basic input data for the development of an adequate model and assessment of the quality of the rock mass, and thus the assessment of the primary support that will ensure the stability of the rock mass during construction. In order to more clearly define the quality of rock mass as a working environment, various classifications have been developed in the world that analyze the influencing factors and give an assessment of the quality of rock mass. Uniaxial compression strength and the influence of groundwater appear as parameters in the RMR classification of rock mass. The paper presents the problems of adequate definition of uniaxial compression strength parameters and influence of groundwater in construction of road tunnels.

Size Effect on the Stability of Tunnel Excavation

2013 ◽  
Vol 838-841 ◽  
pp. 1409-1413
Author(s):  
Xiao Dong Ju ◽  
Chao Shuai Yang ◽  
Yu Jun Zhang
Keyword(s):  
Rock Mass ◽  
Size Effect ◽  
Fractured Rock ◽  
Vertical Displacement ◽  
Tunnel Excavation ◽  
Result Show ◽  
Key Factor ◽  
Dip Angle ◽  
The Stability ◽  
Tunnel Size

Size effect of tunnel excavation in fractured rock mass was analyzed with UDEC in this paper. For simplicity, two series of orthogonal equidistant joints were conceived in the calculation area. Change the excavation size and keep the constitutive model and its parameters of the rock mass around the tunnel to be constant during the solution. The result show, with the increasing of excavation size, vertical displacement of tunnel roof become larger, and the excavation stability turn weaker. So excavation size has great effect on the stability of fractured tunnel. In addition, another key factor, the joint set dip angle, whose effect to the tunnel stability was unearthed by comparing the results of horizontal and 45°joints. The larger the dip angle the weaker the stability at the same tunnel size.

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