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CONTENTS
Volume 14, Number 5, April10 2018
 

Abstract
In order to investigate flow characteristics after water inrush from the working face in process of karst tunnel construction, numerical calculation for two class case studies of water inrush is carried out by using the FLUENT software on the background of Qiyueshan tunnel. For each class water inrush from the tunnel face, five cases under different water-inrush velocity are simulated and researched. Three probing lines are selected respectively in the left tunnel, cross passage, right tunnel and in the height direction of the tunnel centerline. The variation characteristics of velocity and pressure on each probing line under the five water-inrush velocities are analyzed. As for the selected four groups probing lines in the tunnels, the change rules of velocity and pressure on each group probing lines under the same water-inrush velocity are discussed. Finally, the water flow characteristics after inrush from the tunnel face are summarized by comparing the case studies. The results indicate that: (1) The velocity and pressure change greatly at the intersection area of the cross passage and the tunnels. (2) The velocity nearby the tunnel side wall is the minimum, while it is the maximum in the middle position. (3) The pressure value of every cross section in the tunnels is basically fixed. (4) As water-inrush velocity increases, the flow velocity and pressure in the tunnels also increase. The former is approximately proportional to their respective water-inrush velocity, while the latter is not. The research results provide a theoretical basis for making scientific and rational escape routes.

Key Words
karst tunnel; tunnel face; water inrush; velocity and pressure; flow characteristics

Address
J. Wu, S.C. Li, Z.H. Xu, D.D. Pan and S.J. He: Geotechnical and Structural Engineering Research Center, Shandong University, Ji\'nan 250061,Shandong, China

Abstract
In deep mining, the lateral deformation of strip coal pillar appears to be a new characteristic. In order to study the lateral deformation of coal-mass, a monitoring method and monitoring instrument were designed to investigate the lateral deformation of strip coal pillar in Tangkou Coalmine with the mining depth of over 1000 m. Because of without influence of repeated mining, the bedding sandstone roof is easy to break and the angle between maximum horizontal stress and the roadway is small, the maximum lateral deformation is only about 287 mm lower than the other pillars in the same coalmine. In deep mining, the energy accumulation and release cause a discontinuous damage in the heterogeneous coal-mass, and the lateral deformation of coal pillar shows discontinuity, step and mutation characters. These coal-masses not only show a higher plasticity but also the high brittleness at the same time, and its burst tendency is more obvious. According to the monitoring results and theoretical calculations, the yield zone of the coal pillar width is determined as 15.6 m. The monitoring results presented through this study are of great significance to the stability analysis and design of coal pillar.

Key Words
lateral deformation; strip coal pillar in deep mining; field monitoring; step and mutation deformation; yield zone

Address
Shaojie Chen: 1.) State Key Laboratory of Mining Disaster Prevention and Control, Shandong University of Science and Technology, 579 Qianwanggang Road, Huangdao District, Qingdao, Shandong Province, 266590, China
2.) Key Laboratory of Safety and High-efficiency Coal Mining, Ministry of Education, Anhui University of Science and Technology, 168 Taifeng Road, Huainan, Anhui Province, 232001, China

Xiao Qu, Dawei Yin, Xingquan Liu, Hongfa Ma and Huaiyuan Wang: State Key Laboratory of Mining Disaster Prevention and Control, Shandong University of Science and Technology, 579 Qianwanggang Road, Huangdao District, Qingdao, Shandong Province, 266590, China

Abstract
In order to reduce deformation of roadway floor heave in deep underground soft rockmass, four support design patterns were analyzed using the Fast Lagrangian Analysis of Continua (FLAC)3D, including the traditional bolting (Design 1), the bolting with the backbreak in floor (Design 2), the full anchorage bolting with the backbreak in floor (Design 3) and the full anchorage bolting with the bolt-grouting backbreak in floor (Design 4). Results show that the design pattern 4, the full anchorage bolting with the bolt-grouting backbreak in floor, was the best one to reduce the deformation and failure of the roadway, the floor deformation was reduced at 88.38% than the design 1, and these parameters, maximum vertical stress, maximum horizontal displacement and maximum horizontal stress, were greater than 1.69%, 5.96% and 9.97%. However, it was perfectly acceptable with the floor heave results. The optimized design pattern 4 provided a meaningful and reliable support for the roadway in deep underground coal mine.

Key Words
numerical simulation; soft rock roadway; rock bolt supporting; roadway stability

Address
Chunlai Wang, Guangyong Li, Ansen Gao, Feng Shi, Zhijiang Lu and Hui Lu: 1.) Faculty of Resources & Safety Engineering, China University of Mining & Technology Beijing 100083, China
2.) Coal Industry Engineering Research Center of Top-coal Caving Mining, Beijing, 100083, China

Abstract
The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

Key Words
deep mine; gob; unloading; local energy release rate; cusp catastrophe

Address
Jianxin Fu: 1.) School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China
2.) School of Engineering, University of Tokyo, Tokyo 110-0008, Japan

Wei-Dong Song and Yu-Ye Tan: School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China

Abstract
Geomechanical parameters are important factors for engineering projects during design, construction and support stages of tunnel and dam projects. Geostatistical estimation methods are known as one of the most significant approach at estimation of Geomechanical parameters. In this study, Azad dam headrace tunnel is chosen to estimate Geomechanical parameters such as Rock Quality Designation (RQD) and uniaxial compressive strength (UCS) by ordinary kriging as a geostatistical method. Also Rock Mass Rating (RMR) distribution is presented along the tunnel. Main aim in employment of geostatistical methods is estimation of points that unsampled by sampled points.To estimation of parameters, initially data are transformed to Gaussian distribution, next structural data analysis is completed, and then ordinary kriging is applied. At end, specified distribution maps for each parameter are presented. Results from the geostatistical estimation method and actual data have been compared. Results show that, the estimated parameters with this method are very close to the actual parameters. Regarding to the reduction of costs and time consuming, this method can use to geomechanical estimation.

Key Words
geostatistics; geomechanical parameters; tunnelling; ordinary kriging

Address
Ali Aalianvari, Saeed Soltani-Mohammadi and Zeynab Rahemi: Department of Mining Engineering, Faculty of Engineering, University of Kashan, Kashan, Iran

Abstract
By conducting uniaxial loading cycle tests on the coal rock with outburst proneness, the dilatation characteristics at different loading rates were investigated. Under uniaxial loading and unloading, the lateral deformation of coal rock increased obviously before failure, leading to coal dilatation. Moreover, the post-unloading recovery of the lateral deformation was rather small, suggesting the onset of an accelerated failure. As the loading rate increased further, the ratio of the stress at the dilatation critical point to peak-intensity increased gradually, and the pre-peak volumetric deformation decreased with more severe post-peak damage. Based on the laboratory test results, the lateral deformation of the coals at different depths in the #1302 isolated coal pillars, Yangcheng Coal Mine, was monitored using wall rock displacement meter. The field monitoring result indicates that the coal lateral displacement went through various distinct stages: the lateral displacement of the coals at the depth of 2-6 m went through an \"initial increase-stabilize-step up-plateau\" series. When the coal wall of the working face was 24-18 m away from the measuring point, the coals in this region entered the accelerated failure stage; as the working face continued advancing, the lateraldisplacement of the coals at the depth over 6 m increased steadily, i.e., the coals in this region were in the stable failure stage.

Key Words
rock mechanics; different loading rates; stress-strain curve; coal dilatation; lateral deformation

Address
Yangyang Li and Shichuan Zhang: State Key Laboratory of Mining Disaster Prevention and Control, Shandong University of Science and Technology, Shandong 266590, China

Baoliang Zhang: College of Architecture Engineering, Liaocheng University, Shandong 252000, China


Abstract
Estimation of hydraulic parameters is a critical step during design of foundation dewatering works. When many piles are installed in an aquifer, estimation of the hydraulic conductivity should consider the blocking of groundwater seepage by the piles. Based on field observations during a dewatering project in Shanghai, hydraulic conductivities are back-calculated using a numerical model considering the actual position of each pile. However, it is difficult to apply the aforementioned model directly in field due to requirement to input each pile geometry into the model. To develop a simple numerical model and find the optimal hydraulic conductivity, three scenarios are examined, in which the soil mass containing the piles is considered to be a uniform porous media. In these three scenarios, different sub-regions with different hydraulic conductivities, based on either automatic inverted calculation, or on effective medium theory (EMT), are established. The results indicate that the error, in the case which determines the hydraulic conductivity based on EMT, is less than that determined in the automatic inversion case. With the application of EMT, only the hydraulic conductivity of the soil outside the pit should be inverted. The soil inside the pit with its piles is divided into sub-regions with different hydraulic conductivities, and the hydraulic conductivity is calculated according to the volume ratio of the piles. Thus, the use of EMT in numerical modelling makes it easier to consider the effect of piles installed in an aquifer.

Key Words
piles; aquifer; dewatering; hydraulic conductivity; numerical model; EMT

Address
Yao Yuan and Ye-Shuang Xu: 1.) State Key Laboratory of Ocean Engineering and Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration (CISSE), Department of Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2.) Key Laboratory of Land Subsidence Monitoring and Prevention, Ministry of Land and Resources, and Shanghai Engineering Research Center of Land Subsidence, Shanghai 200072, China

Jack S. Shen: 1.) State Key Laboratory of Ocean Engineering and Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration (CISSE), Department of Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2.) Department of Civil and Construction Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia

Bruce Zhi-Feng Wang: Department of Geotechnical and Tunnelling Engineering, School of Highway, Chang

Abstract
In this paper, a comparative study of the effects of soil modelling on the interaction between tunnelling in soft soil and adjacent piled structure is presented. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles as well as tunnel internal forces during the construction of an underground tunnel. The soil is modelled by two material models: the simple, yet approximate Mohr Coulomb (MC) yield criterion; and the complex, but reasonable hardening soil (HS) model with hyperbolic relation between stress and strain. For the former model, two different values of the soil stiffness modulus (E50 or Eur) as well as two profiles of stiffness variation with depth (constant and linearly increasing) were used in attempts to improve its prediction. As these four attempts did not succeed, a hybrid representation in which the hardening soil is used for soil located at the highly-strained zones while the Mohr Coulomb model is utilized elsewhere was investigated. This hybrid representation, which is a compromise between rigorous and simple solutions yielded results that compare well with those of the hardening soil model. The compared results include pile cap movements, pile deformation, and tunnel internal forces. Problem symmetry is utilized and, therefore, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases.

Key Words
tunnelling; soil-structure interaction; piled structure; strain-hardening; finite element; three-dimensional analysis

Address
Ahmed F. Zidan: Department of Civil Engineering, Faculty of Engineering, Beni-Suef University, Salah Salem Street 62511 Beni-Suef, Egypt

Osman M. Ramadan: 1.) Structural Engineering Department, Faculty of Engineering, Cairo University, Giza, Egypt
2.) Higher Technological Institute (HTI), 10th of Ramadan City, Egypt

Abstract
The Earth Mechanics Institute (EMI) was established at the Colorado School of Mines (CSM) in 1974 to develop innovations in rock mechanics research and education. During the last four decades, extensive rock mechanics research has been conducted at the EMI. Results from uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), point load index (PLI), punch penetration (PP), and many other types of tests have been recorded in a database that has been unexamined for research purposes. The EMI database includes over 20,000 tests from over 1,000 different projects including mining and underground construction, and analysis of this database to identify relationships has been started with preliminary results reported here. Overall, statistically significant correlations are identified between bulk density and mechanical strength properties through UCS, BTS, PLI, and PP testing of sedimentary, igneous, and metamorphic rocks. In this paper, bulk density is considered as a surrogate metric that reflects both mineralogy and porosity. From this analysis, sedimentary rocks show the strongest correlation between the UCS and bulk density, whereas metamorphic rocks exhibit the strongest correlation between UCS and PP. Data trends in the EMI database also reveal a linear relationship between UCS and BTS tests. For the singular case of rock coral, the database permits correlations between bulk density of the core versus the deposition depth and porosity. The EMI database will continue under analysis, and will provide additional insightful and comprehensive understanding of the variation and predictability of rock mechanical strength properties and density. This knowledge will contribute significantly toward the increasingly safe and cost-effective geostructures and construction.

Key Words
rock mechanics database; earth mechanics institute (EMI); bulk density, mechanical properties of rock; uniaxial compressive strength (UCS); Brazilian tensile strength (BTS); point load index (PLI), and punch penetration (PP) test

Address
Michael Burkhardt: Department of Mining Engineering, Colorado School of Mines, Golden, Colorado, U.S.A.

Eunhye Kim and Priscilla P. Nelson: 1.) Department of Mining Engineering, Colorado School of Mines, Golden, Colorado, U.S.A.
2.) Center for Underground Construction and Tunneling, Colorado School of Mines, Golden, Colorado, U.S.A.


Abstract
In this paper splitting failure on rock pillars among the underground caverns has been studied. The damaged structure is considered to be thin plates and then the failure mechanism of rock pillars has been studied consequently. The critical load of buckling failure of the rock plate has also been obtained. Furthermore, with a combination of the basic energy dissipation principle, generalized formulas in estimating the number of splitting cracks and in predicting the maximum deflection of thin plate have been proposed. The splitting criterion and the mechanical model proposed in this paper are finally verified with numerical calculations in FLAC 3D.

Key Words
lifecycle performance; stochastic deterioration modelling; structural reliability; reinforcement corrosion; residual strength

Address
Xiaojing Li: 1.) Department of Civil Engineering, Shandong Jianzhu University, Jinan, 250101, China
2.) State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao, 266510, China

Han-Mei Chen: NewRail Centre for Railway Research, Newcastle University, NE1 7RU, U.K.

Yanbo Sun: Shandong Luqiao Group CO. LTD, 250101, China

Rongxin Zhou and Lige Wang: Institute for Infrastructure and Environment, School of Engineering, The University of Edinburgh, EH9 3JL, U.K.


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