scholarly journals A Case Study of Thaumasite Sulfate Attack in Tunnel Engineering

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chongbang Xu ◽  
Xingyu Zhou ◽  
Hualao Wang ◽  
Xiaojing Gao ◽  
Xuefeng Li
Keyword(s):  
Concrete Structure ◽  
Large Scale ◽  
Sulfate Attack ◽  
Surrounding Rock ◽  
Systematic Research ◽  
Mechanism Analysis ◽  
Tunnel Engineering ◽  
Treatment Measures ◽  
Geological Factors ◽  
Structure Collapse

There existed ever-increasing structural diseases in the Dugongling tunnel after the completion of the construction. Systematic research was carried out based on the information of tunnel engineering geology, disease development, mineral composition of surrounding rock and concrete, and laboratory tests. Results showed that (1) the concrete structure from the Dugongling tunnel suffered from a typical thaumasite sulfate attack (TSA); (2) tunnel diseases developed under the influence of multiple geological factors such as groundwater, karst, gypsum bearing stratum, and geological tectonics. Groundwater aggravated the appearance of engineering defects of various geological factors and accelerated the softening and swelling of surrounding rock. Moreover, the additional load of supporting structure increased, and the concrete structure was prone to sulfate attack; (3) the development of tunnel diseases showed long-cycle and large-scale characteristics, and the types of diseases are heterogeneous. The tunnel diseases develop rapidly in the third year after the construction. The structure collapse disease, one of the most serious diseases of tunnel lining, occurred in the fifth year after construction; and (4) according to the conditions of TSA, technical treatment measures were proposed. These measures included blocking the flow of CO 3 2 − , improving the impermeability of concrete structures, and decreasing the diffusion of external ions and groundwater. This work provides a solution for the treatment of similar tunnel disease and mechanism analysis.

scholarly journals Resonance mechanism analysis of large-scale photovoltaic power plant

2021 ◽  
Vol 7 (1) ◽  
pp. 47-54
Author(s):  
Jinjie Lin ◽  
Yong Li ◽  
Sijia Hu ◽  
Qianyi Liu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Power Plant ◽  
Large Scale ◽  
Mechanism Analysis ◽  
Resonance Mechanism ◽  
Photovoltaic Power

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.

Statistical Characteristics and Correlation Analysis for Control Index of Soil-Aggregate Mixture

2013 ◽  
Vol 718-720 ◽  
pp. 1872-1877 ◽  
Author(s):  
Xu Xi Chang ◽  
Xie Jian Ming ◽  
Jiang Ling Fa ◽  
Chen Shan Xiong
Keyword(s):  
Grain Size ◽  
Correlation Analysis ◽  
Normal Distribution ◽  
Large Scale ◽  
Soil Aggregate ◽  
Site Preparation ◽  
Statistical Characteristics ◽  
Coarse Grain ◽  
Systematic Research ◽  
Large Variability

Currently, the soil-aggregate mixture has been widely used in some large-scale site preparation projects, compaction characteristics has been pay more attention by many engineers and researchers. However, systematic research is insufficient on how to choose the filler. Moreover, some industry regulations are different on the requirements about filler. This paper relies on a certain big site preparation projects, discussing statistical characteristics and correlation on the maximal grain size, contents of the coarse grain, gradation and other parameters of soil-aggregate mixture. The results show that the maximal and the median grain size have small discreteness and normal distribution, indicating site filler is easy to reach the requirement; The coefficient of curvature, coefficient of nonuniformity and the coarse grain content have large discreteness, and dont obey normal distribution, indicating the filler has large variability. The median grain size is highly relevant to the coarse grain content; the maximal grain size isnt relevant to the coefficient of nonuniformity, the coefficient of curvature and the coarse grain content. According to the results of correlation analysis, we suggest that the importance order follow by coarse grain content, the maximum grain size and gradation for the control parameters of filler. This research may be significant to other similar projects.

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.

Back Analysis for Mass Parameters of Tunnel Surrounding Rock

2012 ◽  
Vol 170-173 ◽  
pp. 20-24 ◽  
Author(s):  
Kai Cui ◽  
Xue Kai Pan
Keyword(s):  
Deformation Mechanism ◽  
Strain Softening ◽  
Back Analysis ◽  
Surrounding Rock ◽  
Tunnel Engineering ◽  
Railway Tunnel ◽  
Displacement Back Analysis ◽  
Information Construction ◽  
Engineering Information ◽  
The Common

Tunnel engineering information construction has been widely used, and the back analysis is its core. As the common useful method, displacement back analysis is of special advantages. This paper introduces the calculative method based on the application in a railway tunnel. The result shows that strain softening model can be used to simulate the large deformation mechanism of surrounding rock.

scholarly journals Failure Analysis of Intersections of Large-Scale Variable Cross-Section Roadways in Deep Soft Rock and Study of Integrated Control Technology of Bolting and Grouting

2021 ◽  
Author(s):  
Shengrong Xie ◽  
Yiyi Wu ◽  
Dongdong Chen ◽  
Ruipeng Liu ◽  
Xintao Han ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Large Scale ◽  
Integrated Control ◽  
Soft Rock ◽  
Variable Cross Section ◽  
Surrounding Rock ◽  
Variable Cross ◽  
Geological Environment ◽  
Cable Bolt

Abstract In deep underground mining, achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge. Owing to the coupling action of multiple factors such as deep high stress, adjacent faults, cross-layer design, weak lithology, broken surrounding rock, variable cross-sections, wide sections up to 9.9 m, and clusters of nearby chambers, there was severe deformation and breakdown in the No. 10 intersection of the roadway of large-scale variable cross-section at the − 760 m level in the Nanfeng working area of the Wuyang Coal Mine. As there are insufficient examples in engineering methods pertaining to the geological environment described above, the numerical calculation model was oversimplified and support theory underdeveloped; therefore, it is imperative to develop an effective support system for the stability and sustenance of deep roadways. In this study, a quantitative analysis of the geological environment of the roadway through field observations, borehole peeking, and ground stress testing is carried out to establish the FLAC 3D variable cross-section crossing roadway model. This model is combined with the strain softening constitutive (surrounding rock) and Mohr-Coulomb constitutive (other deep rock formations) models to construct a compression arch mechanical model for deep soft rock, based on the quadratic parabolic Mohr criterion. An integrated control technology of bolting and grouting that is mainly composed of a high-strength hollow grouting cable bolt equipped with modified cement grouting materials and a high-elongation cable bolt is developed by analyzing the strengthening properties of the surrounding rock before and after bolting, based on the Heok-Brown criterion. As a result of on-site practice, the following conclusions are drawn: (1) The plastic zone of the roof of the cross roadway is approximately 6 m deep in this environment, the tectonic stress is nearly 30 MPa, and the surrounding rock is severely fractured. (2) The deformation of the roadway progressively increases from small to large cross-sections, almost doubling at the largest cross-section. The plastic zone is concentrated at the top plate and shoulder and decreases progressively from the two sides to the bottom corner. The range of stress concentration at the sides of the intersection roadway close to the passageway is wider and higher. (3) The 7 m-thick reinforced compression arch constructed under the strengthening support scheme has a bearing capacity enhanced by 1.8 to 2.3 times and increase in thickness of the bearing structure by 1.76 times as compared to the original scheme. (4) The increase in the mechanical parameters c and φ of the surrounding rock after anchoring causes a significant increase in σc and σt; the pulling force of the cable bolt beneath the new grouting material is more than twice that of ordinary cement grout, and according to the test, the supporting stress field shows that the 7.24 m surrounding rock is compacted and strengthened in addition to providing a strong foundation for the bolt (cable). On-site monitoring shows that the 60-day convergence is less than 30 mm, indicating that the stability control of the roadway is successful.

scholarly journals MR-Linac Radiotherapy – The Beam Angle Selection Problem

2021 ◽  
Vol 11 ◽  
Author(s):  
Rik Bijman ◽  
Linda Rossi ◽  
Tomas Janssen ◽  
Peter de Ruiter ◽  
Baukelien van Triest ◽  
...  
Keyword(s):  
Treatment Planning ◽  
Large Scale ◽  
Volumetric Modulated Arc Therapy ◽  
Patient Specific ◽  
Systematic Research ◽  
Plan Quality ◽  
Beam Angle ◽  
Clinical Workflow ◽  
Model Case ◽  
Angle Class

BackgroundWith the large-scale introduction of volumetric modulated arc therapy (VMAT), selection of optimal beam angles for coplanar static-beam IMRT has increasingly become obsolete. Due to unavailability of VMAT in current MR-linacs, the problem has re-gained importance. An application for automated IMRT treatment planning with integrated, patient-specific computer-optimization of beam angles (BAO) was used to systematically investigate computer-aided generation of beam angle class solutions (CS) for replacement of computationally expensive patient-specific BAO. Rectal cancer was used as a model case.Materials and Methods23 patients treated at a Unity MR-linac were included. BAOx plans (x=7-12 beams) were generated for all patients. Analyses of BAO12 plans resulted in CSx class solutions. BAOx plans, CSx plans, and plans with equi-angular setups (EQUIx, x=9-56) were mutually compared.ResultsFor x>7, plan quality for CSx and BAOx was highly similar, while both were superior to EQUIx. E.g. with CS9, bowel/bladder Dmean reduced by 22% [11%, 38%] compared to EQUI9 (p<0.001). For equal plan quality, the number of EQUI beams had to be doubled compared to BAO and CS.ConclusionsComputer-generated beam angle CS could replace individualized BAO without loss in plan quality, while reducing planning complexity and calculation times, and resulting in a simpler clinical workflow. CS and BAO largely outperformed equi-angular treatment. With the developed CS, time consuming beam angle re-optimization in daily adaptive MR-linac treatment could be avoided. Further systematic research on computerized development of beam angle class solutions for MR-linac treatment planning is warranted.

scholarly journals To increase trust, change the social design behind aggregated biodiversity data

Database ◽  
2018 ◽  
Vol 2018 ◽  
Author(s):  
Nico M Franz ◽  
Beckett W Sterner
Keyword(s):  
Large Scale ◽  
Syntactic Structure ◽  
Original Data ◽  
Quality Data ◽  
Systematic Research ◽  
Aggregation Process ◽  
Biodiversity Data ◽  
Social Design ◽  
The Social ◽  
Accountability Gap

Abstract Growing concerns about the quality of aggregated biodiversity data are lowering trust in large-scale data networks. Aggregators frequently respond to quality concerns by recommending that biologists work with original data providers to correct errors ‘at the source.’ We show that this strategy falls systematically short of a full diagnosis of the underlying causes of distrust. In particular, trust in an aggregator is not just a feature of the data signal quality provided by the sources to the aggregator, but also a consequence of the social design of the aggregation process and the resulting power balance between individual data contributors and aggregators. The latter have created an accountability gap by downplaying the authorship and significance of the taxonomic hierarchies—frequently called ‘backbones’—they generate, and which are in effect novel classification theories that operate at the core of data-structuring process. The Darwin Core standard for sharing occurrence records plays an under-appreciated role in maintaining the accountability gap, because this standard lacks the syntactic structure needed to preserve the taxonomic coherence of data packages submitted for aggregation, potentially leading to inferences that no individual source would support. Since high-quality data packages can mirror competing and conflicting classifications, i.e. unsettled systematic research, this plurality must be accommodated in the design of biodiversity data integration. Looking forward, a key directive is to develop new technical pathways and social incentives for experts to contribute directly to the validation of taxonomically coherent data packages as part of a greater, trustworthy aggregation process.

scholarly journals Application of Constant Resistance and Large Deformation Anchor Cable in Soft Rock Highway Tunnel

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Xiaoming Sun ◽  
Bo Zhang ◽  
Li Gan ◽  
Zhigang Tao ◽  
Chengwei Zhao
Keyword(s):  
Large Deformation ◽  
Support System ◽  
Field Tests ◽  
Soft Rock ◽  
Internal Force ◽  
Surrounding Rock ◽  
Gansu Province ◽  
Tunnel Engineering ◽  
Anchor Cable ◽  
Constant Resistance

Muzhailing Highway Extra-long Tunnel in Lanzhou, Gansu Province, China, belongs to the soft rock tunnel in the extremely high geostress area. During the construction process, large deformation of the soft rock occurred frequently. Taking the no. 2 inclined shaft of Muzhailing tunnel as the research object, an NPR (negative Poisson’s ratio) constant resistance and large deformation anchor cable support system based on high prestress force, constant resistance, and releasing surrounding rock pressure was proposed. The characteristics of the surrounding rock under the steel arch support and NPR anchor cable support were compared and analyzed by using 3DEC software. A series of field tests were conducted in the no. 2 inclined shaft, and the rock strength, displacement of the surrounding rock, deep displacement of the surrounding rock, internal force of steel arch, and axial force of anchor cable were measured to study the application effect of the NPR anchor cable support system in tunnel engineering. Moreover, the 3DEC numerical simulation results were compared with the field test results. The research results show that the application of NPR constant resistance and large deformation anchor cable support system in tunnel engineering has achieved good results, and it plays a significant role in controlling the large deformation of the tunnel surrounding rock.

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