Chemical injection application at tunnel service shaft to prevent ground settlement induced by groundwater drainage: A case study

Chemical injections are used in a variety of applications in civil and mining engineering, including ground stabilization, support anchoring, strata sealing, reduction and diversion of groundwater flow and water ingress, and creation of a load-bearing ring during tunneling. Historically, injection application without pressure was first employed by the Romans. Polyurethane injections have been used in coal mines to stabilize roofs and to reduce problems regarding water ingress in shafts and tunnels. This paper focuses on chemical injection, which was employed to prevent ground settlement induced by groundwater drainage from the shaft. As a result of the drainage of 4.5 l/s groundwater from the Shaft 4, which was sunk for service at Guzelyali station of Izmir Metro Project, the groundwater level dropped 4 m from the original level, and ground settlement reached 98 mm, while the inner tunnel vertical convergence was 23 mm. This can be explained with the closure of pore volumes in the overburden. Ground settlement was stopped and groundwater level approached its original level after chemical injection.     

Synthesis of boron/nitrogen substituted carbons for aqueous asymmetric capacitors

Boron/nitrogen substituted carbons were synthesized by co-pyrolysis of polyborazylene/coal tar pitch blends to yield a carbon with a boron and nitrogen content of 14 at% and 10 at%, respectively. The presence of heteroatoms in these carbons shifted the hydrogen evolution overpotential to −1.4 V vs Ag/AgCl in aqueous electrolytes, providing a large electrochemical potential window (∼2.4 V) as well as a specific capacitance of 0.6 F/m². An asymmetric capacitor was fabricated using the as-prepared low surface area carbon as the negative electrode along with a redox active manganese dioxide as the positive electrode. The energy density of the capacitor exceeded 10 Wh/kg at a power density of 1 kW/kg and had a cycle life greater than 1000 cycles.     

The role of umbrella arch and face bolt as deformation preventing support system in preventing building damages

Ground settlement is the most significant environmental impact of the tunnels excavated in intensively urbanized regions. A Considerable amount of ground settlement occurs by pre-convergence, formed during the time of support setting followed by the excavation, and movement of tunnel face into the tunnel. The risk of damage on the buildings by the ground settlement can be catastrophically high. Therefore, rock engineers bear an important duty to prevent the potential damage on buildings by controlling the ground settlement while excavating the tunnels. This has been accomplished by applying umbrella arch with face bolt technique recently in various important areas. In this method, the ground settlements can substantially be decreased by limiting the tunnel face movement into the tunnel, by creating a pseudo shell around the tunnel face with umbrella arch and then increasing the stability with face bolts. In this study, as part of the 2nd phase of Izmir metro construction in densely populated Poligon district of Izmir the effects of umbrella arch-face bolt applications on ground settlements have been determined using numerical modeling and in situ measurements. Results indicated that the umbrella arch and face bolt applications have significantly diminished the risk of settlement damage on buildings by reducing the ground settlements and convergence as 69% and 57%, respectively.     

Estimation of limit angle using laminated displacement discontinuity analysis in the Soma coal field, Western Turkey

Determination of the limit angle at the Manisa-Soma-Eynez coal field, a major coal production area in Turkey, is difficult because of the presence of a landslide caused by the waste from a neighboring open-pit site being dumped over the underground mine at the Soma-Eynez basin. In fact, it is not possible to determine the effect of extraction on the surface from field studies. Thus, in order to determine the limit angle, in-situ subsidence measurements, geophysical measurements, rock-based tests in the laboratory and the data obtained from a physical model have supported numerical modeling studies. The software, LAMODEL, used for the numerical modeling was developed by National Institute for Occupational Safety and Health (NIOSH), and is based on the Boundary Element Method. The results obtained from modeling have been found to be compatible with other studies and as a result the limit angle has been determined.     

Optimization of downhole pump setting depths in liquid-dominated geothermal systems: A case study on the Balcova-Narlidere field,Turkey

Downhole pumps are being used increasingly more often in low-enthalpy geothermal wells. The depth at which these pumps are installed depends on the physical and chemical characteristics of the geothermal fluid, the production flow rate, and the reservoir pressure and permeability. In this study we have investigated the factors affecting pump setting depths in low-temperature, liquid-dominated geothermal systems and defined the relationship between flow rate and pressure drawdown based on multi-rate test results. The methodology proposed was applied to the Balcova-Narlidere geothermal field, Turkey. It was found that the most important parameters for determining the capacity and setting depth of a downhole pump were flow performance, non-condensable gas concentration, and temperature. The implementation of the methodology is illustrated.     

Effect of heat treatment on physical properties of CdO films deposited by sol–gel method

CdO film has been deposited by sol–gel spin coating method on the glass substrate and then the film has been annealed at 400, 500, 600 °C for 1 h. Effect of annealing temperature on the structural and optical properties of the film has been investigated. The crystal structure and orientation of the as-grown and annealed CdO films have been investigated by X-ray diffraction method. Annealed CdO films are polycrystalline with (111) preferential orientation. The information on strain and grain size is obtained from the full width-at-half-maximum (FWHM) of the diffraction peaks. Texture coefficient and lattice constant have been calculated. The surface morphology of the films has been analyzed. The optical band gap value decreased with increasing the annealing temperatures.