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Rock excavation techniques
Published in Ömer Aydan, Rock Mechanics and Rock Engineering, 2019
Breaker is a powerful percussion hammer fitted to an excavator for breaking rocks. It is powered by an auxiliary hydraulic or pneumatic system from the excavator, which is fitted with a foot-operated valve for this purpose. They are generally used when blasting cannot be used due to safety or environmental issues (Figure 6.63).
Estimation of impulsive forces of hydraulic breaker via transfer path analysis (TPA) method
Published in Ömer Aydan, Takashi Ito, Takafumi Seiki, Katsumi Kamemura, Naoki Iwata, 2019 Rock Dynamics Summit, 2019
Changheon Song, Daeji Kim, Sang-Seuk Kweon, Joo-Young Oh, Jin-Young Park, Jong-Hyoung Kim, Jung-Woo Cho
The hydraulic breaker operates by converting the energies of the hydraulic pressure and nitrogen gas into the kinetic energy of the striking pistons. The kinetic energy is then delivered to the rock via the chisel, thereby breaking it. The hydraulic breaker in this study strikes the steel plate (Figure 3) to create uniform impulsive forces. The setup and adjustments ensured the repeatability and reproducibility of the experiment, and minimized variations in the impulsive forces caused by the compressive strength of the rock. The setup also excluded any effects caused by the inhomogeneity and anisotropy of the rock.
Simulation-based framework for optimal construction equipment allocation considering construction noise emissions
Published in Journal of Asian Architecture and Building Engineering, 2023
Hoyoung Baek, Seunghoon Jung, Juwon Hong, Taehoon Hong
Next, the accuracy of the noise level calculated based on the WebCYCLONE simulation was verified (refer to Figures 5 and 6). The Leq for 8 hours measured at the construction site was 77.77 dB. Meanwhile, the execution time of one piece of construction equipment inside the construction site, which was calculated with the WebCYCLONE simulation to estimate the noise exposure level, was 8.29 h for a breaker, 4.67 h for an excavator, 1.21 h for a crawler crane, and 0.04 h for a dump truck, respectively. Based on the results, the estimated Leq of one construction equipment for the measurement point was calculated using Eq. (2) and (3), and it was calculated at 77.56 dB for a breaker, 65.96 dB for an excavator, 61.84 dB for a crawler crane, and 40.50 dB for a dump truck, respectively. In particular, although the execution time per unit of the breaker was 3.62 h less than that of the excavator, the Leq of the breaker was 11.60 dB higher than that of the excavator because the sound pressure level generated by the breaker was larger than that of the excavator. As a result, the noise level synthesized at the measurement point according to the input quantity of each construction equipment using Eq. (4) was 80.75 dB, which is an overestimated value of 2.98 dB (3.83%) for the measured noise level compared to the measured noise level.
Key criteria influencing the choice of Arctic shipping: a fuzzy analytic hierarchy process model
Published in Maritime Policy & Management, 2018
Po-Hsing Tseng, Kevin Cullinane
The descriptions of the various sub-criteria and the sources which justify their potential influence (and inclusion in the model therefore) are shown for each of the key criteria in Tables 1–4. As can be seen in Figure 3, the criterion ‘Economic Factors’ includes five sub-criteria, namely: fuel costs, crew costs, insurance, other transit costs and sailing time. The ‘Technical Factors’ criterion comprises four sub-criteria, namely: ice breaker, ship construction, navigation and communication. The ‘Political Factors’ criterion consists of three sub-criteria, namely: right of navigation, maritime conventions and stakeholders’ concerns. Finally, the ‘Safety Factors’ criterion includes four sub-criteria, namely: weather and geographic complexity, risk of crew health and safety, search and rescue, and environmental concerns. As pointed out earlier in the paper, the allocation of specific sub-criteria to each of the four key criteria is based on the outcomes of an extensive review of the literature. It should be clear, however, that the potential for dependence between the four key criteria is quite significant; for example, the need for ice-strengthened ships (a technical factor) will obviously have an economic impact in terms of increased costs of ship construction and fuel use (Solakivi, Kiiski, and Ojala 2017). This potential problem of dependence between key criteria is largely overcome, however, by further disaggregation in the ensuing analysis to focus on the sub-criteria.
The White House Station of the Grand Paris Express Project
Published in Structural Engineering International, 2020
Yi Zhang, Stéphane Commend, Quentin Martin-Lavigne, Jérôme Lacoste
Steel-lined shafts were chosen to demolish existing structures, build the connection structure, and excavate the tunnel (Fig. 6). The tunnel was constructed by means of conventional methods. Limestone was excavated with a point attack machine such as a hydraulic rock breaker, and plastic clays were excavated by an excavator with a bucket. Mucking was carried out by load–haul–dump machines and trucks. A bridge crane was used to evacuate cuttings of the tunnel from the TN2 shaft. Earthworks of the connection structure were carried out in the open air, and earthworks of the station were carried out in a top–down fashion.