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The aim of this paper is to evaluate the different rock supports that have been installed in road tunnels of Tehran-Shomal freeway of Iran to choose efficiency rock supports from economic point of view. Tunnels pass through the Karaj green Tuff that moderately weathered and fractured with interlocked joint set in most part. Factor of safety using finite difference code, FLAC and RocSupport software is compared. The plastic zone radius and maximum displacement around the two D-shape tunnels are determined and new support system is proposed. In this project, the excavation and support system were not based on NATM or "build as you go" so the pre-deigned support by consultant engineers was challenged. According to the numerical stability analysis and monitoring of tunnels during excavation, it was observed that the four meters long rockbolts with twenty centimeter of shotcrete cover and lattice girders should be replaced with slightly light support include three meters long rockbolts and ten centimeters of shotcrete cover.
ABSTRACT "Moshampa" is one of Iran's large dams under construction. The rock slopes facing the dam diversion tunnels failed during excavation. Site investigations and primary kinematic analyses showed that the mode of instability has been blocky toppling failure. The slope inclination was decreased and the portal was reconstructed with a new design. Since, according to the same investigations, the geological conditions of the rock mass in the portals of the power-house and diversion tunnels are similar, the slopes facing the dam power-house tunnels may also fail during excavation; so, they should be checked against blocky toppling failure. In this paper, a brief review of toppling failures of Moshampa dam has been given first. Then, the stability analyses of the portals of the diversion tunnels and their stabilization method have been checked by Goodman-Bray analytical approach under dry conditions. Finally, the stability of the slope, facing the portals of the power-house tunnels, has been checked against blocky toppling by the method and its stable inclination computed.
Stresses and a Failure Mode from Physical and Numerical Models of Undercut Slope Lying on Inclined Bedding Plane
Leelasukseree, Cheowchan (Chiang Mai University) | Pipatpongsa, Thirapong (Tokyo Institute of Technology) | Khosravi, Mohammad Hossein (Tokyo Institute of Technology) | Mavong, Narongsak (Tokyo Institute of Technology)
ABSTRACT An 80-m high low wall slope at Mae Moh mine, Lampang, Thailand, sits on a low friction interface between an under burden claystone and a thin clay layer called G1. By 2012, the slope must be partially undercut for mining, approximately 1 million tons of lignite. Stability of the sizable slope will be questionable when being undercut and mined. To study the behaviors of the undercut slope lying on an inclined bedding plane, a number of physical models and numerical models are studied. For the physical models, a 1.0 m × 0.45 m × 0.80 m (W×H×D) undercut slope model was constructed by using humid sand, acrylic and an aluminum work frame, low friction Teflon sheet as a smooth interface and sand paper adhered with acrylic plate as side supports. Moist sand physical properties, its strength and all interface frictions were experimentally determined beforehand. Five potentiometers and a camera were installed and employed to monitor and digitally record the crest and the slope face displacements. Stresses in various locations and directions are also measured by installing eight pressure gauges. Concurrently, the numerical model of the undercut slope is created based on the physical model dimensions and the moist sand properties, strength and its interface frictions. 3DEC®, a three dimensional discrete element program, is selected for simulating and studying the behavior of the undercut slope. The behaviors of the undercut slope examined from both physical and numerical models have shown similar tendencies toward measured displacements and stresses during undercutting. Moreover, the buckling failure mode of both slope models is discovered excitedly. The results provide further understandings of the undercut slope behaviors. The better understandings help engineers to design and monitor the undercut slope.
- Geology > Geological Subdiscipline > Stratigraphy (0.85)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.71)
ABSTRACT In this paper, Melen Bosphorus Tunnel Project, the geological characteristics of Bosphorus Tunnel's location and some information about the selected machine are presented in general. In İstanbul, 685 million m of surface water (dams, lakes and dikes) and 30 million m of ground water for a total of 715 million m of drinking water is being produced. In addition, by use of Istranca Streams, 235 million m of water is supplied in annual average. In İstanbul, the annual reel consumption of gross water per capita is 235 liters per day. According to İstanbul Water and Sewerage Works' master plan by the year 2040, foreseen consumption of 276 liters water per capita, to meet the needs of 11 million population per day, 1.1 billion m of water was needed. However in 2005, this population was accessed, and the city's population has been growing rapidly since then. Considering the population growth rate with the data current; in 2025, Istanbul's population is estimated to exceed 22 million, and it is clear that water resources, close to city of İstanbul would not be sufficient, when the population growth is taken into account. In this regard, Yeşilçay System was put into service on 31 May 2003, in order to meet Istanbul's urgent water need as soon as possible. Thanks to Melen System, planned for meeting İstanbul's long term drinking and service water need, city's water requirement shall be met by 2040 with 268 million m (8,5 m /sn) water supply per year at the first stage and 1180 billion m water supply per year at the end of the third stage. Bosphorus Tunnel, starts from the Ayazağa Entrance, diameter of 6.15 m, constructed beneath 135 m. sea level, 5551-m-long, continues with the slope of 7.4 % along 2347 m, and then continues horizantally with the slope of 0.14 % along 1081 m, finally in 145 m. deep, tunnel reaches the shaft, diameter of 8.1.Tunnel has been excavated by TDM, whose trademark is Herrenknecht and which could be started up with the both off mode (EPB) and on mode.
- Water & Waste Management > Water Management > Water Supplies & Services (1.00)
- Energy (1.00)
ABSTRACT There are so many technical aspects related to tunneling in weak rock because of encountering rock mechanics problem such as high strain rate, squeezing,…together with practical problems. Tunneling in this condition requires the considerable use of a combination of support systems such as shotcrete, rock bolts, wire mesh and steel sets to stabilize the tunnel. Using of top heading and benching down excavation method in large cross section tunnels, stability of support systems installed in heading section while executing benching step is one of important issue which has to be taken to account. In this study, several methods for benching in weak ground condition have been studied and the method used in long penstock tunnels of Roudbar dam waterway as a case study has been explained. The method including excavation of two side wall of benching section beneath crown support system and filling excavated area with reinforced concrete piles has been investigated through numerical models using FLAC2D software. Results show that using piling system, deformation of tunnel wall and displacements of crown support decrease comparing to benching without additional treatment. But according to horizontal displacement magnitudes, it would be better to use another additional support such as invert struts combined with piling for completely controlling of horizontal displacements.
- Asia > Middle East > Iran (0.52)
- Europe (0.47)
- Materials (0.51)
- Government > Military > Army (0.47)
- Construction & Engineering (0.37)
- Well Drilling (0.92)
- Management > Professionalism, Training, and Education > Communities of practice (0.61)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.61)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.49)
Challenges of Design and Construction of a Highway Tunnel through Mixed Geology in Himalayas
Goel, R.K. (Central Institute of Mining & Fuel Research) | Dwivedi, R.D. (Central Institute of Mining & Fuel Research) | Viswanathan, G. (Chenani-Nashri Tunnelway Ltd) | Rathore, J.S. (Chenani-Nashri Tunnelway Ltd)
ABSTRACT The Government of India has entrusted the National Highway Authority of India (NHAI) with the responsibility of four laning of Chenani to Nashri Section of NH-1A from km 89.00 to km 130.00 including 9km long bi-directional traffic tunnel with a parallel escape tunnel of 9km on BOT (annuity) basis. The project area lies in western Himalayan region. The rock masses along the project of the Chenani-Nashri tunnel, belong to the Lower Murree formation that includes a sequence of interbedded sandstones, siltstones and claystones layers. The tunnel behaviour classification of the rock mass has been performed by Geodata, Italy. These rock behaviour classes has been correlated with the rock mass behavior type of NATM. The supports for various behavior classes have also been designed using the numerical methods as per the requirements. The tunnel construction work was started in August 2011 from South end and in September 2011 from North end. As expected the experience of tunneling in Himalayan mixed geology having bands of sandstone, siltstone, claystone, intermingled siltstone and claystone and sheared siltstone and claystone is not very encouraging. There have been instances of overbreaks and cracks in shotcrete support in the tunnel. Accordingly the designs have been modified. The benefits of displacements/convergence monitoring have been highlighted at the end.
- Energy > Oil & Gas > Upstream (0.68)
- Government > Regional Government > Asia Government > India Government (0.54)
ABSTRACT Tunnel stability should be estimated and expressed by two curial points, tunnel deformationand stress distribution of rock mass around tunnel, through theoretical studies(Gioda, G.and Locatelli, L., 1999; Sterpi., D., 1999; Kim, Sang-Hwan, 2003) and many case studues(Song et al., 2002; Wang,Yi-Wan,2001) on tunnel deformation analysis until the recent. For the first point, some hybrid analysis was proposed by a conjugated method about the critical strain analysis by Sakurai(1988,1990,1997), 3D numerical simulation, field measurement on tunnel excavation, and stability analysis of stress-strain relation based on elastic theory.For the second point, recently successful cases on tunnel excavationin South Korea were introduced. Also, as an new approach about 2 arch conventional tunnel, positive effects of pre-supporting system were respectively introduced relating to the conventional method. Thekey items about the utilization of field measurement on tunnel coustruction and the choice of tunnel excavation methodon primary design were conclusionally summaried and suggested.
ABSTRACT Based on a series of laboratory tests and in situ monitoring and tests at deep tunnels excavated by TBM or D&B method, mechanism of evolution process of different types of rockburst, including strain burst, strain-structure slip rockburst, immediate rockburst and time delayed rockburst, and has been understood. The digital borehole televiewer and seismicity monitoring system have been used to obverse cracking initiation and propagation process during rock burst evolution process. A warning system based on micro seismicity has been established for warning of various intensities of rockbursts, such as slight, moderate, intensive and extremely intensive rockbursts. The probability with the intensity of rockburst is also given. The strategy for excavation and support design has been recommended for various intensities of rokcburst before the excavation. The strategy for dynamic control of rockburst evolution process is also proposed according the warning. The methodology has been successfully applied to rockburst risk reduction for deep tunnels at Jinping II hydropower station. The results have illustrated applicability of the proposed methodology and techniques on rockburst.
ABSTRACT There are methods and applications for assessing the stability of caverns during the construction period. However, little focus is paid to the maintenance for existing caverns. A maintenance method for existing caverns is focused in this paper and proposed. The continuous monitoring data on the deformation and/or the stress situation of the supports and the surrounding rock are utilized to elaborate a numerical model that fits the current mechanical condition of the cavern. Then using the numerical model, the future behavior of the cavern is simulated under the possible risks, involving the deterioration of the surrounding rock and/or PS anchors. The maintenance criteria are established for the future behavior of the existing cavern based on the results with the comparison to the critical state of the material forming the cavern and the surrounding rock. These processes are summarized as the maintenance flow-chart for the existing caverns.
- Energy > Renewable > Hydroelectric (0.41)
- Energy > Power Industry > Utilities (0.41)
ABSTRACT We used the Smoothed Particle Hydrodynamics (SPH) method, which is a type of particle method, to numerically simulate the water jet (WJ) excavation of rock. The results can be summarized as follows:We developed code for the three-dimensional numerical simulation of the WJ excavation of rock. To verify the usefulness of this simulation code, we performed a laboratory experiment that involved rock excavation by WJ. We proposed five types of failure criteria in the simulation of WJ excavation by SPH. The tensile strain criterion, which is based on the tensile strain between a particle and a neighboring particle, was consistent with the experimental results. This criterion was considered to most closely approximate the mechanism of WJ excavation. To remove fractured rock particles from the wall of the borehole, we used repulsive force between the fractured particles and unfractured particles of rock in the case of the tensile strain criterion. Our results verified that the fractured particles were drained from the borehole.