scholarly journals Experimental Analysis of Deformation Mechanics and Stability of a Shallow-Buried Large-Span Hard Rock Metro Station

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Wei Li ◽  
Jiwen Bai ◽  
Kexian Li ◽  
Shijie Zhang
Keyword(s):  
Model Test ◽  
Large Scale ◽  
Hard Rock ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Three Dimensional Model ◽  
Metro Station ◽  
Large Span ◽  
Deformation Mechanics ◽  
Primary Support

Based on a certain Qingdao metro station, a large-scale three-dimensional model test has been carried out to investigate the stability of the surrounding rock masses (hard rock) and a large-span metro station under different excavation methods and technologies. The model test includes an entire section excavation, an arch-cover excavation, and a primary support arch-cover excavation. Compared with the entire section excavation, the primary support arch-cover method can effectively control the vault settlement and clearance convergence deformation of the surrounding rock masses, reducing them by 15–30%. The deformation itself goes through three stages: slow, abrupt, and stable. The excavation of the “middle hole” creates a drastic change in the tunnel vault during the arch-cover excavation; however, the timely application of supports can effectively constrain the range of disturbance caused by the excavation and weaken the degree of load agglomeration of the surrounding rock masses.

scholarly journals Key Factors Affecting the Deformation and Failure of Surrounding Rock Masses in Large-Scale Underground Powerhouses

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Meng Wang ◽  
Jia-wen Zhou ◽  
An-chi Shi ◽  
Jin-qi Han ◽  
Hai-bo Li
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Affecting Factors ◽  
Key Factors ◽  
Underground Powerhouse ◽  
Deformation And Failure ◽  
Factors Affecting ◽  
Geological Conditions

The stability of the surrounding rock masses of underground powerhouses is always emphasized during the construction period. With the general trends toward large-scale, complex geological conditions and the rapid construction progress of underground powerhouses, deformation and failure issues of the surrounding rock mass can emerge, putting the safety of construction and operation in jeopardy and causing enormous economic loss. To solve these problems, an understanding of the origins and key affecting factors is required. Based on domestic large-scale underground powerhouse cases in the past two decades, key factors affecting the deformation and failure of the surrounding rock mass are summarized in this paper. Among these factors, the two most fundamental factors are the rock mass properties and in situ stress, which impart tremendous impacts on surrounding rock mass stability in a number of cases. Excavation is a prerequisite of surrounding rock mass failure and support that is classified as part of the construction process and plays a pivotal role in preventing and arresting deformation and failure. Additionally, the layout and structure of the powerhouse are consequential. The interrelation and interaction of these factors are discussed at the end of this paper. The results can hopefully advance the understanding of the deformation and failure of surrounding rock masses and provide a reference for design and construction with respect to hydroelectric underground powerhouses.

scholarly journals Model Test of Anchoring Effect on Zonal Disintegration in Deep Surrounding Rock Masses

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Xu-Guang Chen ◽  
Qiang-Yong Zhang ◽  
Yuan Wang ◽  
De-Jun Liu ◽  
Ning Zhang
Keyword(s):  
Model Test ◽  
Surrounding Rock ◽  
Zonal Disintegration ◽  
Formation Condition ◽  
Anchor Effect ◽  
Rock Masses ◽  
Tunnel Excavation ◽  
Anchoring Effect ◽  
Tension And Compression ◽  
Deep Rock

The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D geomechanics model test was conducted to research the anchoring effect of zonal disintegration. The model was constructed with anchoring in a half and nonanchoring in the other half, to compare with each other. The optical extensometer and optical sensor were adopted to measure the displacement and strain changing law in the model test. The displacement laws of the deep surrounding rocks were obtained and found to be nonmonotonic versus the distance to the periphery. Zonal disintegration occurs in the area without anchoring and did not occur in the model under anchoring condition. By contrasting the phenomenon, the anchor effect of restraining zonal disintegration was revealed. And the formation condition of zonal disintegration was decided. In the procedure of tunnel excavation, the anchor strain was found to be alternation in tension and compression. It indicates that anchor will show the nonmonotonic law during suppressing the zonal disintegration.

scholarly journals Study on Deflection of Surrounding Rock Force Chain and Disaster Mechanism of Instability in Deep Stope

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Guang-Xiang Xie ◽  
Anying Yuan ◽  
Lei Wang
Keyword(s):  
Large Scale ◽  
Vertical Direction ◽  
Surrounding Rock ◽  
Horizontal Direction ◽  
Force Chain ◽  
Force Chains ◽  
Rock Masses ◽  
Working Face ◽  
The Stability ◽  
Overburden Strata

The mechanism of force chain deflection and instability-caused disaster in the deep surrounding rock of large-scale stopes was examined in this study using theoretical analyses, laboratory experiments, PFC3D numerical simulations, and other comprehensive research methods based on a discrete element theory that included force chain research as the main line. The results indicated that the overburden strata of the stope presented an arched force chain in both the strike and the inclined direction of the working face. In addition, a force chain shell composed of strong chains similar to “ellipsoid” in shape had been formed in the overburden strata space of the entire stope. The main mechanical characteristics of the force chain shell were as follows: the strength levels of the force chains within the shell were the largest; the strength levels of the force chains inside and outside the shell were relatively low and had evolved with the advancement of the working face; the directions of the force chains in different areas of the surrounding rock masses of the stope were deflected, forming an anisotropic characteristic with a certain deflection angle which was distributed in the vertical direction at the shell base; the force chains at the shell shoulder were angled in the horizontal direction, and the force chain at the shell top had an obvious horizontal direction; finally, the strong chain clusters of the surrounding rock masses of the stope formed a force chain shell in the stope space, and the stress shell was the macroscopic embodiment of the force transference in the force chain shell formed by the force chain clusters, which revealed not only the mechanical mechanism of the force chain shell formed by the surrounding rock but also the relationship between the macro stress shell and the stress chain shell. The stability of the shell determines the stability of the surrounding rock, and the instability of the shell will lead to dynamic disasters such as strong dynamic pressure or rock burst.

scholarly journals Floor Heave Mechanism and Anti-Slide Piles Control Technology in Deep and Large-Span Chamber

2021 ◽  
Vol 11 (10) ◽  
pp. 4576
Author(s):  
Jian Shi ◽  
Desen Kong
Keyword(s):  
Model Test ◽  
Shear Failure ◽  
Deformation Mode ◽  
Control Technology ◽  
Plastic Limit ◽  
Large Span ◽  
Similarity Model ◽  
Floor Heave ◽  
Plastic Limit Analysis ◽  
Local Shear

Based on plastic limit analysis, the deformation and fracture mechanism of the floor in the large-span chambers of deep mines are discussed and a similarity model test is carried out to verify the reliability of the theoretical analysis. The results show that the local shear failure first appears below the loading area and develops to the middle part of the test model with the increase in load; when the local shear failure develops to form a continuous sliding surface, continuous plastic flow deformation occurs; the distribution of the plastic zone and the deformation mode obtained from the similarity model test are basically consistent with the Hill-like deformation mode derived from plastic limit analysis. A control technology with anti-slide piles is proposed in order to deal with floor heave in large-span chambers on the basis of previous work. An approach for determining the supporting parameters of anti-slide piles is deduced. To deal with the floor heave in the −1100 level gangue winch room of the Huafeng Coal Mine, a comprehensive reinforcement scheme with anti-slide piles composed of discarded rails and anti-floating anchors is introduced for the floor heave control of the chambers. Site monitoring results show that the scheme not only effectively restrains the development of floor heave, but also ensures the long-term stability of the chamber floor.

scholarly journals Potential Use of Organic- and Hard-Rock Mine Wastes on Aided Phytostabilization of Large-Scale Mine Tailings under Semiarid Mediterranean Climatic Conditions: Short-Term Field Study

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Claudia Santibañez ◽  
Luz María de la Fuente ◽  
Elena Bustamante ◽  
Sergio Silva ◽  
Pedro León-Lobos ◽  
...  
Keyword(s):  
Mine Tailings ◽  
Large Scale ◽  
Management Practices ◽  
Hard Rock ◽  
Mine Waste ◽  
Organic Amendments ◽  
Dry Weight ◽  
Climatic Conditions ◽  
Goat Manure ◽  
Site Rehabilitation

The study evaluated the efficacy of organic- and hard-rock mine waste type materials on aided phytostabilization of Cu mine tailings under semiarid Mediterranean conditions in order to promote integrated waste management practices at local levels and to rehabilitate large-scale (from 300 to 3,000 ha) postoperative tailings storage facilities (TSFs). A field trial with 13 treatments was established on a TSF to test the efficacy of six waste-type locally available amendments (grape and olive residues, biosolids, goat manure, sediments from irrigation canals, and rubble from Cu-oxide lixiviation piles) during early phases of site rehabilitation. Results showed that, even though an interesting range of waste-type materials were tested, biosolids (100 t ha-1dry weight, d.w.) and grape residues (200 t ha-1d.w.), either alone or mixed, were the most suitable organic amendments when incorporated into tailings to a depth of 20 cm. Incorporation of both rubble from Cu-oxide lixiviation piles and goat manure into upper tailings also had effective results. All these treatments improved chemical and microbiological properties of tailings and lead to a significant increase in plant yield after three years from trial establishment. Longer-term evaluations are, however required to evaluate self sustainability of created systems without further incorporation of amendments.

scholarly journals Potential of Flocculant-Aided Soil Slurry Dewatering in Land Reclamation: Laboratory Investigations

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Yang Jiao ◽  
Jia He ◽  
Peiyuan Zhou ◽  
Ziqian Cao
Keyword(s):  
Model Test ◽  
Large Scale ◽  
Land Reclamation ◽  
Drainage Water ◽  
Tube Model ◽  
Soil Slurry ◽  
Vacuum Preloading ◽  
Geotextile Tube ◽  
Laboratory Investigations ◽  
Flocculation Effect

When soil slurry is used as a fill material in land reclamation projects, vacuum preloading or geotextile tube systems are often adopted for the dewatering treatment in a large scale. However, these two methods often suffer from clogging problems and impede further dewatering treatment. In this study, we test the potential of using flocculants to enhance the dewatering efficiency in a vacuum preloading model test and a geotextile tube model test. Experimental results show that, by adding a flocculant into soil slurry, the dewatering efficiency in terms of drainage volumes and rates is significantly improved as compared to that in pure soil slurry. The amounts of drainage water in the tests with flocculant addition are about 20% and 100% more than those in pure slurry tests in the vacuum preloading and geotextile tube model tests, respectively. The underlying reason could be the flocculation effect that prevents the movement of small soil grains and the formation of impermeable layers on the filters.

scholarly journals Experimental Study on the Ratio of Similar Materials in Weak Surrounding Rock Based on Orthogonal Design

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Pengfei Jiao ◽  
Xiao Zhang ◽  
Xinzhi Li ◽  
Bohong Liu ◽  
Haojie Zhang
Keyword(s):  
Model Test ◽  
Orthogonal Design ◽  
Surrounding Rock ◽  
Similar Material ◽  
Geomechanical Model ◽  
Geomechanical Model Test ◽  
Geological Conditions ◽  
Key Factor ◽  
Similar Materials ◽  
Weak Surrounding Rock

In the aspect of stability analysis of tunneling engineering, geomechanical model test is an important research method. A similar material is the prerequisite for the success of geomechanical model test. In the field of major engineering applications, a variety of similar materials are prepared for different geological conditions of surrounding rock and applied in some major engineering. With the use of standard sand, fine sand, and silt clay as materials, similar materials for weak surrounding rock were developed. Based on the orthogonal design method, through the direct shear test, the range analysis and variance analysis of various factors affecting the physical and mechanical parameters of weak surrounding rock are carried out. The results show similar material can meet the requirements in weak surrounding rock. Standard sand is the key factor that influences the internal friction angle of similar materials, and silt clay is the key factor affecting the cohesion of similar materials. Similar materials can meet the elastic modulus and severe requirements of the weak surrounding rock and can be used for the weak surrounding rock engineering. The new type of similar material configuration is widely used in shallow buried tunnel entrance section and urban shallow buried excavation engineering, in addition to tunnel engineering in loess stratum, and the problems of engineering design and construction are solved through geomechanical model test.

Study on Deformation and Damage of Rock Mass Subject to High In Situ Stress by Using a Elastoplastic Damage Model and Considering the Impact of Weak Planes

2013 ◽  
Vol 838-841 ◽  
pp. 705-709
Author(s):  
Yun Hao Yang ◽  
Ren Kun Wang
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Damage Model ◽  
Back Analysis ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
High In Situ Stress ◽  
Underground Caverns ◽  
The Impact

Large scale underground caverns are under construction in high in-situ stress field at Houziyan hydropower station. To investigate deformation and damage of surrounding rock mass, a elastoplastic orthotropic damage model capable of describing induced orthotropic damage and post-peak behavior of hard rock is used, together with a effective approach accounting for the presence of weak planes. Then a displacement based back analysis was conducted by using the measured deformation data from extensometers. The computed displacements are in good agreement with the measured ones at most of measurement points, which confirm the validities of constitutive model and numerical simulation model. The result of simulation shows that damage of surrounding rock mass is mainly dominated by the high in-situ stress rather than the weak planes and heavy damage occur at the cavern shoulders and side walls.

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