Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).05
Ngan Minh Vu
The rapid development in the economy and the urban population in cities in Vietnam in recent years leads to dramatic growth in traffic congestion, noise and air pollution, and environmental degradation. Urban underground infrastructure thus becomes an inevitable solution since the surface space becomes too expensive and restricted in spite of the high cost of tunnel construction. However, tunnelling in deltaic urban areas, in particular in the cases of Mekong Delta and Red River Delta areas, often faces to difficulties of soft soil conditions and the existence of important historical buildings on the surface. The first metro line constructed in Vietnam from Ben Thanh to Suoi Tien, which is located under crowded areas of Hochiminh city, was tunnelled in such conditions. This paper presents a back analysis for the stability of the tunnelling process in the project. The minimum support pressures is estimated by using the wedge model proposed by Jancsecz, S., & Steiner, W. (1994). Meanwhile, the maximum support pressure is estimated by the blow-out model proposed by Vu et al. (2016). Based on these results, the range of support pressures recommended for the Earth Pressure Balance Tunnel Boring Machine in the Hochiminh Metro Line No.1 project soft soil conditions is derived and compared to in situ support pressures obtained from the monitoring data in this tunnelling project. The study result shows a good agreement between the support pressures obtained from stability analysis models and the monitoring data from the construction site. Based on this back analysis, some recommendations are proposed with the purpose of successful construction in the next tunnelling projects in Hochiminh city.
{"title":"Stability analysis when tunnelling in soft soil condition in Hochiminh city","authors":"Ngan Minh Vu","doi":"10.46326/jmes.2022.63(3a).05","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).05","url":null,"abstract":"The rapid development in the economy and the urban population in cities in Vietnam in recent years leads to dramatic growth in traffic congestion, noise and air pollution, and environmental degradation. Urban underground infrastructure thus becomes an inevitable solution since the surface space becomes too expensive and restricted in spite of the high cost of tunnel construction. However, tunnelling in deltaic urban areas, in particular in the cases of Mekong Delta and Red River Delta areas, often faces to difficulties of soft soil conditions and the existence of important historical buildings on the surface. The first metro line constructed in Vietnam from Ben Thanh to Suoi Tien, which is located under crowded areas of Hochiminh city, was tunnelled in such conditions. This paper presents a back analysis for the stability of the tunnelling process in the project. The minimum support pressures is estimated by using the wedge model proposed by Jancsecz, S., & Steiner, W. (1994). Meanwhile, the maximum support pressure is estimated by the blow-out model proposed by Vu et al. (2016). Based on these results, the range of support pressures recommended for the Earth Pressure Balance Tunnel Boring Machine in the Hochiminh Metro Line No.1 project soft soil conditions is derived and compared to in situ support pressures obtained from the monitoring data in this tunnelling project. The study result shows a good agreement between the support pressures obtained from stability analysis models and the monitoring data from the construction site. Based on this back analysis, some recommendations are proposed with the purpose of successful construction in the next tunnelling projects in Hochiminh city.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121923142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).09
N. T. Pham, C. Nguyen
It is very important to study the stability of the tunnel in the area affected by mining activities. In particular, the choice of coal pillar size has a direct influence on the stability of these tunnels. The authors of this study used the Flac3D program to model a mining face LC1 with various coal pillar sizes. The 220 m-long mining face known as LC1 has 20 degrees rock mass layers. The studied coal pillars are various widths at 5 m, 8 m, 10 m, 15 m, 20 m, and 30 m. The highest vertical stress and maximum horizontal stress are placed at different locations along the lower mining face (LC2), as shown by the results of the numerical simulation. The pressure distribution of the rock mass on the tunnel's top and the level of stress concentration on its two sides are asymmetrical for inclined seam conditions. The position of the maximum vertical tension is expected to change from the left hip to the side of the coal pillar as the coal pillar widens. This change essentially marks the system's transition from one stable state to another. Due to the rock mass's weak stability during this transition, the support must be strengthened in order to improve the rock stability.
{"title":"Numerical analysis of the influence of coal pillar size on auxiliary tunnel stability","authors":"N. T. Pham, C. Nguyen","doi":"10.46326/jmes.2022.63(3a).09","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).09","url":null,"abstract":"It is very important to study the stability of the tunnel in the area affected by mining activities. In particular, the choice of coal pillar size has a direct influence on the stability of these tunnels. The authors of this study used the Flac3D program to model a mining face LC1 with various coal pillar sizes. The 220 m-long mining face known as LC1 has 20 degrees rock mass layers. The studied coal pillars are various widths at 5 m, 8 m, 10 m, 15 m, 20 m, and 30 m. The highest vertical stress and maximum horizontal stress are placed at different locations along the lower mining face (LC2), as shown by the results of the numerical simulation. The pressure distribution of the rock mass on the tunnel's top and the level of stress concentration on its two sides are asymmetrical for inclined seam conditions. The position of the maximum vertical tension is expected to change from the left hip to the side of the coal pillar as the coal pillar widens. This change essentially marks the system's transition from one stable state to another. Due to the rock mass's weak stability during this transition, the support must be strengthened in order to improve the rock stability.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129799193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).08
T. Dang, Minh Tuan Tran, H. Nguyen
Ground Characteristic Curve (GCC) describes the relationship between the initial stress of rock mass and the displacement of rock mass on the boundary of tunnels. Another way that indicates the relationship of support pressure and the level of Convergence Confinement of tunnels by percent. The using GCC to design supports in the underground construction has many advantages to ensure full utilization of the loading bearing capacity of rock mass, and release a part of initial stress in the rock mass around tunnels. However, this method is limited in the field of underground mines in Viet Nam. This article analyzed and applied GCC and Convergence Confinement Method (CCM) to design the supports of underground constructions and applied them to the geological conditions of the Nam Mau coal mine - Vinacomin. The research results show that at the geological conditions of the drift at level +125 in Nam Mau coal mine, TH section steel ribs with flange width 124 mm, section depth 108 mm, weight 21 kg/m, maximum support pressure 1.98 MPa, and spacing 700 mm were applied. Results of research in this method can be applied to design rock supports for deep roadways and other drifts in the underground mines in Quang Ninh province of Viet Nam. By a factor of safety, mobilized support pressure, wall displacement of roadways, and convergence of roadways the designation and selection of rock support around roadways will become clearer. Near future this method should be widely applied in the combined protection design in deep roadways in underground mines in Viet Nam. Although the method has great advantages, it is still necessary to have complete and detailed monitoring data of the geological and hydrogeological conditions in the area under consideration.
{"title":"Ground Characteristic Curve and Convergence Confinement Method - A case study","authors":"T. Dang, Minh Tuan Tran, H. Nguyen","doi":"10.46326/jmes.2022.63(3a).08","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).08","url":null,"abstract":"Ground Characteristic Curve (GCC) describes the relationship between the initial stress of rock mass and the displacement of rock mass on the boundary of tunnels. Another way that indicates the relationship of support pressure and the level of Convergence Confinement of tunnels by percent. The using GCC to design supports in the underground construction has many advantages to ensure full utilization of the loading bearing capacity of rock mass, and release a part of initial stress in the rock mass around tunnels. However, this method is limited in the field of underground mines in Viet Nam. This article analyzed and applied GCC and Convergence Confinement Method (CCM) to design the supports of underground constructions and applied them to the geological conditions of the Nam Mau coal mine - Vinacomin. The research results show that at the geological conditions of the drift at level +125 in Nam Mau coal mine, TH section steel ribs with flange width 124 mm, section depth 108 mm, weight 21 kg/m, maximum support pressure 1.98 MPa, and spacing 700 mm were applied. Results of research in this method can be applied to design rock supports for deep roadways and other drifts in the underground mines in Quang Ninh province of Viet Nam. By a factor of safety, mobilized support pressure, wall displacement of roadways, and convergence of roadways the designation and selection of rock support around roadways will become clearer. Near future this method should be widely applied in the combined protection design in deep roadways in underground mines in Viet Nam. Although the method has great advantages, it is still necessary to have complete and detailed monitoring data of the geological and hydrogeological conditions in the area under consideration.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126569802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).10
Doan Viet Dao
The process of excavating roadway, shafts, and exploiting coal seams located near the ground may cause subsidence of the ground surface, cracking, damage to structures on the surface. Therefore, it is necessary to rely on the specific conditions of the site to calculate and forecast the level of impact on the works on the surface, ground subsidence when excavated roadway, shafts, exploiting coal seams located near the ground. Based on the topographical conditions, geological hydrogeological conditions and current status of works on the surface, the technical design of the excavation of the twin inclined shafts from +30÷-300 levels in the Ha Lam coal mine is proposed. This paper uses the numerical method by FLAC3D software to build the model with a height of 450 m and a width of 700 m to study the effect of the twin inclined shafts construction on the deformation of rock mass on the ground surface. This research has shown that after the construction of the twin inclined shafts from +30÷-300 levels, the area of each inclined shaft is 15.8 m2, rock mass on the ground surface is deformed, the maximum value of vertical deformation is about 5 cm, horizontally deformation is about 3 cm, the effect range of deformation the surface is within a radius of 25 m. So on the +30 level of Ha Lam coal mines when constructing works serving the coal mining within a radius of 25 m in the twin inclined shafts entrance area, it is necessary to consider the impact excavation of the twin inclined shafts. But when constructing works outside a radius of 25 m in the twin inclined shafts entrance area will not be affected. Recommendations for the Ha Lam coal mine process need to install more deformation monitoring stations to monitor the deformation process of the surface of +30 level when excavation of the twin inclined shafts.
{"title":"Behavior of twin inclined shafts excavated for +30 levels surface stability in Ha Lam coal mine","authors":"Doan Viet Dao","doi":"10.46326/jmes.2022.63(3a).10","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).10","url":null,"abstract":"The process of excavating roadway, shafts, and exploiting coal seams located near the ground may cause subsidence of the ground surface, cracking, damage to structures on the surface. Therefore, it is necessary to rely on the specific conditions of the site to calculate and forecast the level of impact on the works on the surface, ground subsidence when excavated roadway, shafts, exploiting coal seams located near the ground. Based on the topographical conditions, geological hydrogeological conditions and current status of works on the surface, the technical design of the excavation of the twin inclined shafts from +30÷-300 levels in the Ha Lam coal mine is proposed. This paper uses the numerical method by FLAC3D software to build the model with a height of 450 m and a width of 700 m to study the effect of the twin inclined shafts construction on the deformation of rock mass on the ground surface. This research has shown that after the construction of the twin inclined shafts from +30÷-300 levels, the area of each inclined shaft is 15.8 m2, rock mass on the ground surface is deformed, the maximum value of vertical deformation is about 5 cm, horizontally deformation is about 3 cm, the effect range of deformation the surface is within a radius of 25 m. So on the +30 level of Ha Lam coal mines when constructing works serving the coal mining within a radius of 25 m in the twin inclined shafts entrance area, it is necessary to consider the impact excavation of the twin inclined shafts. But when constructing works outside a radius of 25 m in the twin inclined shafts entrance area will not be affected. Recommendations for the Ha Lam coal mine process need to install more deformation monitoring stations to monitor the deformation process of the surface of +30 level when excavation of the twin inclined shafts.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130824329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).11
Viet Huy Le ., Nhan Thi Pham ., A. N. Pham, Tien Manh Le
The crack of the concrete in underground constructions is generally difficult to detect and repair and consequently causes structural deterioration. Smart concrete with self-healing ability to autonomously repair micro cracks is a potential smart material to apply for underground constructions with sustainable development proposes. This paper reviews healing materials, the self-healing process, and the mixing method of self-healing concretes using bacteria, mineral admixtures, and fibers. The bacteria such as Bacillus sphaericus, Bacillus megaterium, Bacillus subtilis, Bacillus pasteurii, and Bacillus subtilis can produce a calcareous product for healing exterior cracks through microbial metabolic processes. As micro cracks are formed in the smart concrete, the bacteria spores contact nutrients and water and generate Calcium Carbonate (CaCO3). The addition of mineral admixtures based on silica including fly ash and granulated blast furnace slag (GGBS) heals the inner cracks through Calcium silicate hydrate (CSH) gels ( hydration reaction products. Other minerals such as expansive materials, geo-materials, crystals, and chemical additives change their forms or volumes to close cracks. Fibers including steel, carbon, PVA, PE, and carbon fibers are utilized to develop self-healing concretes based on controlling the crack width. The addition of fibers generates multiple micro-cracks, decreases the crack width, and enhances autogenous crack healing. Besides, healing agents can be easily dispersed into self-healing concretes by using the dry mixing, the wet mixing, or the latter mixing. Hence, all smart concretes with self-healing ability demonstrate potential and suitable characteristics for underground constructions. A combination method of fibers and bacteria or mineral admixtures can be applied for better sealing crack and durability enhancement of underground concrete structures.
{"title":"Self-healing concrete: a potential smart material to apply for underground construction","authors":"Viet Huy Le ., Nhan Thi Pham ., A. N. Pham, Tien Manh Le","doi":"10.46326/jmes.2022.63(3a).11","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).11","url":null,"abstract":"The crack of the concrete in underground constructions is generally difficult to detect and repair and consequently causes structural deterioration. Smart concrete with self-healing ability to autonomously repair micro cracks is a potential smart material to apply for underground constructions with sustainable development proposes. This paper reviews healing materials, the self-healing process, and the mixing method of self-healing concretes using bacteria, mineral admixtures, and fibers. The bacteria such as Bacillus sphaericus, Bacillus megaterium, Bacillus subtilis, Bacillus pasteurii, and Bacillus subtilis can produce a calcareous product for healing exterior cracks through microbial metabolic processes. As micro cracks are formed in the smart concrete, the bacteria spores contact nutrients and water and generate Calcium Carbonate (CaCO3). The addition of mineral admixtures based on silica including fly ash and granulated blast furnace slag (GGBS) heals the inner cracks through Calcium silicate hydrate (CSH) gels ( hydration reaction products. Other minerals such as expansive materials, geo-materials, crystals, and chemical additives change their forms or volumes to close cracks. Fibers including steel, carbon, PVA, PE, and carbon fibers are utilized to develop self-healing concretes based on controlling the crack width. The addition of fibers generates multiple micro-cracks, decreases the crack width, and enhances autogenous crack healing. Besides, healing agents can be easily dispersed into self-healing concretes by using the dry mixing, the wet mixing, or the latter mixing. Hence, all smart concretes with self-healing ability demonstrate potential and suitable characteristics for underground constructions. A combination method of fibers and bacteria or mineral admixtures can be applied for better sealing crack and durability enhancement of underground concrete structures.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130603189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).04
Minh Tuan Tran, T. N. Do, Phong Duyen Nguyen
Placement of infrastructure and other facilities underground brings superior opportunities for long-term improvements in terms of the environmental impact of urban areas and more efficient use of underground space. However, underground construction in urban areas is a high-risk activity and has been considered a challenging problem for geotechnical and structural designers. Therefore, the evaluation of the stability of underground structures plays a vital role in structural and construction design. This paper presents a case study on analyzing the stability of steel piles walls and tunnels excavated by shield machines in the urban area in Vietnam in terms of the change in internal forces in the structures. The research results show that the excavated stages of the basement influence on the values of internal force in the tunnel lining. In the case of study using composite lining in the tunnel, the thickness of lining concrete 35 cm, steel frame type I-W1000×883 are applied for tunnel excavated before construction of nearby basement, and 30 cm and W1000×350 steel ribs for the opposite side. This research could be applied to evaluate the effects of tunnel excavation near the existing structures in urban such as in the geological conditions in the Ha Noi and Ho Chi Minh City in the near future. However, this analysis also has the disadvantage that it does not consider the construction time as well as the construction sequence of the works during tunnel excavation. The shapes of the tunnel only are circular tunnels and the only type of steel piles in this research. Further study, total evaluation for other types of tunnels and walls of basements should be considered.
将基础设施和其他设施置于地下，为长期改善城市地区的环境影响和更有效地利用地下空间带来了优越的机会。然而，城市地区的地下建设是一项高风险的活动，一直被认为是岩土工程和结构设计师面临的一个具有挑战性的问题。因此，地下结构的稳定性评价在结构和施工设计中起着至关重要的作用。本文以越南城市地区盾构机开挖的钢桩、墙和隧道为例，从结构内力变化的角度分析其稳定性。研究结果表明，基坑开挖阶段对衬砌内力值有一定的影响。以隧道复合式衬砌为研究对象，附近地下室施工前开挖的隧道衬砌混凝土厚度为35 cm，钢架型号为I-W1000×883，对面为30 cm, W1000×350钢肋。研究结果可用于评价河内、胡志明市等城市既有构筑物附近隧道开挖的地质条件。然而，这种分析也有缺点，即没有考虑隧道开挖过程中工程的施工时间和施工顺序。隧道的形状仅为圆形隧道，也是本研究中唯一的钢桩类型。进一步研究，应考虑其他类型隧道及地下室墙体的综合评价。
{"title":"Stability of steel pile walls and tunnels excavated by shield machines in the urban areas: A case study","authors":"Minh Tuan Tran, T. N. Do, Phong Duyen Nguyen","doi":"10.46326/jmes.2022.63(3a).04","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).04","url":null,"abstract":"Placement of infrastructure and other facilities underground brings superior opportunities for long-term improvements in terms of the environmental impact of urban areas and more efficient use of underground space. However, underground construction in urban areas is a high-risk activity and has been considered a challenging problem for geotechnical and structural designers. Therefore, the evaluation of the stability of underground structures plays a vital role in structural and construction design. This paper presents a case study on analyzing the stability of steel piles walls and tunnels excavated by shield machines in the urban area in Vietnam in terms of the change in internal forces in the structures. The research results show that the excavated stages of the basement influence on the values of internal force in the tunnel lining. In the case of study using composite lining in the tunnel, the thickness of lining concrete 35 cm, steel frame type I-W1000×883 are applied for tunnel excavated before construction of nearby basement, and 30 cm and W1000×350 steel ribs for the opposite side. This research could be applied to evaluate the effects of tunnel excavation near the existing structures in urban such as in the geological conditions in the Ha Noi and Ho Chi Minh City in the near future. However, this analysis also has the disadvantage that it does not consider the construction time as well as the construction sequence of the works during tunnel excavation. The shapes of the tunnel only are circular tunnels and the only type of steel piles in this research. Further study, total evaluation for other types of tunnels and walls of basements should be considered.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127730355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).02
V. V. Pham, Anh Ngoc Do, Hung Trong Vo, Daniel Dias, Thanh Chi Nguyen, Do Xuan Hoi
Tunnels are an important component of the transportation and utility system of cities. They are being constructed at an increasing rate to facilitate the need for space expansion in densely populated urban areas and mega-cities. The circular and rectangular tunnels cannot completely meet the requirements of underground space exploitation regarding the cross-section. Sub-rectangular tunnels are recently used to overcome some drawbacks of circular and rectangular tunnels in terms of low utilization space ratio and stress concentration, respectively. However, the behavior of the sub-rectangular tunnels under seismic loading is still limited. This need to be regarded and improved. This paper focuses on conducting a numerical analysis to study the behavior of the sub-rectangular tunnels under seismic loadings. Here seismic loadings in this study are represented by quasi-static loadings. Based on the numerical model of the circular tunnel that was validated by comparison with analytical solutions, the numerical model of the sub-rectangular tunnel is created. This paper is devoted to highlight the differences between the behavior of the sub-rectangular tunnels compared with the circular ones subjected to quasi-static loadings. The soil-lining interaction, i.e., full slip and no-slip conditions are particularly considered. The influence of soil’s Young’s modulus on the sub-rectangular tunnel behavior under quasi-static loading is also investigated. The results indicated that soil’s Young’s modulus significantly affects static, incremental, and total internal forces in the tunnel lining under quasi-static loadings. Special attention is a significant difference in total internal forces in the sub-rectangular tunnel lining in comparison with the circular tunnel ones and the stability of the lining tunnel for both the full slip and no-slip conditions when subjected to quasi-static loadings.
{"title":"Effect of soil Young’s modulus on Sub-rectangular tunnels behavior under quasi-static loadings","authors":"V. V. Pham, Anh Ngoc Do, Hung Trong Vo, Daniel Dias, Thanh Chi Nguyen, Do Xuan Hoi","doi":"10.46326/jmes.2022.63(3a).02","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).02","url":null,"abstract":"Tunnels are an important component of the transportation and utility system of cities. They are being constructed at an increasing rate to facilitate the need for space expansion in densely populated urban areas and mega-cities. The circular and rectangular tunnels cannot completely meet the requirements of underground space exploitation regarding the cross-section. Sub-rectangular tunnels are recently used to overcome some drawbacks of circular and rectangular tunnels in terms of low utilization space ratio and stress concentration, respectively. However, the behavior of the sub-rectangular tunnels under seismic loading is still limited. This need to be regarded and improved. This paper focuses on conducting a numerical analysis to study the behavior of the sub-rectangular tunnels under seismic loadings. Here seismic loadings in this study are represented by quasi-static loadings. Based on the numerical model of the circular tunnel that was validated by comparison with analytical solutions, the numerical model of the sub-rectangular tunnel is created. This paper is devoted to highlight the differences between the behavior of the sub-rectangular tunnels compared with the circular ones subjected to quasi-static loadings. The soil-lining interaction, i.e., full slip and no-slip conditions are particularly considered. The influence of soil’s Young’s modulus on the sub-rectangular tunnel behavior under quasi-static loading is also investigated. The results indicated that soil’s Young’s modulus significantly affects static, incremental, and total internal forces in the tunnel lining under quasi-static loadings. Special attention is a significant difference in total internal forces in the sub-rectangular tunnel lining in comparison with the circular tunnel ones and the stability of the lining tunnel for both the full slip and no-slip conditions when subjected to quasi-static loadings.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114370023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).06
Hung Trong Vo, K. V. Dang, Anh Ngoc Do, T. N. Do
Geotechnical problems are complicated to the extent and cannot be expected in other areas since non-uniformities of existing discontinuous, pores in materials and various properties of the components. At present, it is extremely difficult to develop a program for tunnel analysis that considers all complicated factors. However, tunnel analysis has made remarkable growth over the past several years due to the development of numerical analysis methods and computer development, given the situation that it was difficult to solve the formula of elasticity, viscoelasticity, and plasticity for the dynamic feature of the ground when the constituent laws, yielding conditions of ground materials, geometrical shape and boundary conditions of the structure were simulated in the past. Actual problems have been successfully analyzed in addition to simple analysis and more reasonable design and construction management materials have been obtained. The stability of rock mass around an underground large cavern is the key to the construction of large-scale underground projects which have to divide into different parts stages. Rock bolt and shotcrete are important means to ensure the stability of the underground cavern. The objective of the paper is to evaluate the stability of a large cavern in the Cai Mep project in Ba Ria- Vung Tau by numerical method. The results from numerical simulations show that the stability of rock support of the cavern is in fair agreement with the original design calculation. The maximum displacement of rock mass surrounding caverns, maximum compressive stress and tensile stress in shotcrete, and the maximum axial force of rock bolt obtained by Rocscience -RS2- Phase2 software are the main parameters in the stability assessment.
{"title":"Study on the stability of rock mass around large underground cavern based on numerical analysis: A case study in the Cai Mep project","authors":"Hung Trong Vo, K. V. Dang, Anh Ngoc Do, T. N. Do","doi":"10.46326/jmes.2022.63(3a).06","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).06","url":null,"abstract":"Geotechnical problems are complicated to the extent and cannot be expected in other areas since non-uniformities of existing discontinuous, pores in materials and various properties of the components. At present, it is extremely difficult to develop a program for tunnel analysis that considers all complicated factors. However, tunnel analysis has made remarkable growth over the past several years due to the development of numerical analysis methods and computer development, given the situation that it was difficult to solve the formula of elasticity, viscoelasticity, and plasticity for the dynamic feature of the ground when the constituent laws, yielding conditions of ground materials, geometrical shape and boundary conditions of the structure were simulated in the past. Actual problems have been successfully analyzed in addition to simple analysis and more reasonable design and construction management materials have been obtained. The stability of rock mass around an underground large cavern is the key to the construction of large-scale underground projects which have to divide into different parts stages. Rock bolt and shotcrete are important means to ensure the stability of the underground cavern. The objective of the paper is to evaluate the stability of a large cavern in the Cai Mep project in Ba Ria- Vung Tau by numerical method. The results from numerical simulations show that the stability of rock support of the cavern is in fair agreement with the original design calculation. The maximum displacement of rock mass surrounding caverns, maximum compressive stress and tensile stress in shotcrete, and the maximum axial force of rock bolt obtained by Rocscience -RS2- Phase2 software are the main parameters in the stability assessment.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121780710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).13
Phong Duyen Nguyen, Minh Tuan Tran, Thuc V. Ngo, L. Tang, Tung Huu Trinh
Steel Fiber-Reinforced Concrete (SFRC) is an advanced material studied and used in some developed countries in the world in recent years. The characteristics of this concrete are intensive compression, high tensile and tolerance strength, higher repeated loads, and long-term durable stability. Steel fibers were used to manufacture SFRC because of their outstanding characteristics. The durability of SFRC should be improved and the disadvantages of traditional concrete should be reduced. To produce inserts in the support structure, SFRC must be applied. Because 60÷70% of tunnels are being constructed for underground coal mines of Vietnam National Coal and Mineral Group (TKV) currently use. SPV steel frame support in combination with reinforced concrete inserts steel. To increase the plaque's capacity and durability in the future, a study must be done to create new, very intense concrete materials. This study investigated how the ratio and compressive strength of steel fibers affected the flexural characteristics of SRFC. To achieve this, 30 MPa strength SFRC with 0.5%, 1.0%, and 1.5% fiber fractions were made and evaluated. This study’s experimental results can be summarized as follows: according to the compression experimental results, the compressive strength and elastic modulus of SFRC were not considerably impacted by the steel fiber volume ratio; The experimental results from the bending tests show that for concrete with a strength of 30 MPa, the proportion of steel fibers of 1.0% has higher flexural strength and toughness than the proportion of steel fibers of 0.5% and 1.5%; A comparison of the test at 28 days of age with the (ACI 211.1-91, 1991) was completely satisfied.
{"title":"Application of steel fiber-reinforced concrete for slab lagging at underground mines in Quang Ninh","authors":"Phong Duyen Nguyen, Minh Tuan Tran, Thuc V. Ngo, L. Tang, Tung Huu Trinh","doi":"10.46326/jmes.2022.63(3a).13","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).13","url":null,"abstract":"Steel Fiber-Reinforced Concrete (SFRC) is an advanced material studied and used in some developed countries in the world in recent years. The characteristics of this concrete are intensive compression, high tensile and tolerance strength, higher repeated loads, and long-term durable stability. Steel fibers were used to manufacture SFRC because of their outstanding characteristics. The durability of SFRC should be improved and the disadvantages of traditional concrete should be reduced. To produce inserts in the support structure, SFRC must be applied. Because 60÷70% of tunnels are being constructed for underground coal mines of Vietnam National Coal and Mineral Group (TKV) currently use. SPV steel frame support in combination with reinforced concrete inserts steel. To increase the plaque's capacity and durability in the future, a study must be done to create new, very intense concrete materials. This study investigated how the ratio and compressive strength of steel fibers affected the flexural characteristics of SRFC. To achieve this, 30 MPa strength SFRC with 0.5%, 1.0%, and 1.5% fiber fractions were made and evaluated. This study’s experimental results can be summarized as follows: according to the compression experimental results, the compressive strength and elastic modulus of SFRC were not considerably impacted by the steel fiber volume ratio; The experimental results from the bending tests show that for concrete with a strength of 30 MPa, the proportion of steel fibers of 1.0% has higher flexural strength and toughness than the proportion of steel fibers of 0.5% and 1.5%; A comparison of the test at 28 days of age with the (ACI 211.1-91, 1991) was completely satisfied.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123425539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-31DOI: 10.46326/jmes.2022.63(3a).12
K. V. Dang, Hung Trong Vo, Hao Doan Ngo, Huy Xuan Tran
In 2020, Vietnam has 25 thermal power plants in operation, emitting a total amount of fly ash and coal bottom ash of about 13 million tons/year. It makes increasing the costs of landfill space, and negatively affect the environment. The major goal of this study is to recommend an optimal amount of thermal power plant fly ash to be added to the concrete mix to create concrete lagging for the SVP steel arches of the underground coal mine in the Quang Ninh region. In order to lower the cost of drift support and improve the efficiency of environmental protection, fly ash is used in this study to make concrete lagging in place of cement to the extent of 30%. This study also demonstrates a recent development in the use of novel materials to construct rock/soil supports for underground mines in Vietnam. use of fly ash in concrete as a partial replacement for cement is more important today. The comparison of strength properties of concrete laggings by experimental study at the Laboratory of underground construction between two concrete lagging types at Hanoi University of Mining and Geology (HUMG) will show the benefits in terms of the strength of concrete lagging using fly ash. The paper also presents the results of an experimental study on using fly ash for making concrete lagging at the Laboratory. The comparison of the drift support using concrete laggings in SVP steel arches fly ash-made products and conventional underground mining support will aid in demonstrating the benefits of employing fly ash. From the study's findings, it can be inferred that fly ash can substitute cement in lower classes of construction concrete such as M200.
{"title":"An experimental study on the use of fly ash for making concrete lagging of SVP steel arches in underground coal mines in Quang Ninh area","authors":"K. V. Dang, Hung Trong Vo, Hao Doan Ngo, Huy Xuan Tran","doi":"10.46326/jmes.2022.63(3a).12","DOIUrl":"https://doi.org/10.46326/jmes.2022.63(3a).12","url":null,"abstract":"In 2020, Vietnam has 25 thermal power plants in operation, emitting a total amount of fly ash and coal bottom ash of about 13 million tons/year. It makes increasing the costs of landfill space, and negatively affect the environment. The major goal of this study is to recommend an optimal amount of thermal power plant fly ash to be added to the concrete mix to create concrete lagging for the SVP steel arches of the underground coal mine in the Quang Ninh region. In order to lower the cost of drift support and improve the efficiency of environmental protection, fly ash is used in this study to make concrete lagging in place of cement to the extent of 30%. This study also demonstrates a recent development in the use of novel materials to construct rock/soil supports for underground mines in Vietnam. use of fly ash in concrete as a partial replacement for cement is more important today. The comparison of strength properties of concrete laggings by experimental study at the Laboratory of underground construction between two concrete lagging types at Hanoi University of Mining and Geology (HUMG) will show the benefits in terms of the strength of concrete lagging using fly ash. The paper also presents the results of an experimental study on using fly ash for making concrete lagging at the Laboratory. The comparison of the drift support using concrete laggings in SVP steel arches fly ash-made products and conventional underground mining support will aid in demonstrating the benefits of employing fly ash. From the study's findings, it can be inferred that fly ash can substitute cement in lower classes of construction concrete such as M200.","PeriodicalId":170167,"journal":{"name":"Journal of Mining and Earth Sciences","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122153941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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