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Design Criteria for Drill Rigs
Published in C.P. Chugh, Ken Steele, V.M. Sharma, Design Criteria for Drill Rigs: Equipment and Drilling Techniques, 2020
C.P. Chugh, Ken Steele, V.M. Sharma
The air chamber, also called the surge chamber, must be installed on top of this high-pressure line to absorb the peak pressure and cushion the flow. The basic operation of this chamber is to compress air trapped inside it. A chamber hung upside down from the bottom of the line will definitely not trap air. The top of the chamber is usually fitted with a plug. If this plug leaks water, this means that there is no air trapped inside and, consequently, the advantage of the surge chamber is nil.
Damage mechanism and stability analysis of rock mass in the high geo-stress tunnel subjected to excavation
Published in Geomatics, Natural Hazards and Risk, 2022
Quanfu Ding, Biao Li, Haijian Su, Nuwen Xu, Xuehua Li, Xingyang Deng
The deformation and failures of high geostress tunnels are usually influenced by a variety of factors including high geostress, excavation unloading, geological structures, etc. Rock mass damage evolution mechanism dominated by different factors is fundamental for stability analysis. The traffic tunnel of tailrace surge chamber of Shuangjiangkou Hydropower station was in high in-situ stress environment and the rock mass strength is between 60 Mpa and 80 Mpa, and the ratio of ground stress to rock mass strength is between 0.25 and 0.5. Rock burst phenomenon is very easy to occur. During the construction of similar tunnels at Shuangjiangkou Hydropower Station, the problems of block falling and rock burst frequently occurred. In addition, the conditions of further deterioration of surrounding rock mass quality, such as weak structural plane and construction support tunnel excavation, were involved in the traffic tunnel of tailwater pressure regulating chamber from Stake K0 + 0 − K0 + 250. Therefore, microseismic monitoring was carried out in this section of tunnel to provide technical support for on-site construction safety. In the past, many scholars studied the stability of tunnel surrounding rock by microseismic monitoring technology. And the influence of structural plane or group hole effect was considered singly. However, the influence of the them on the stability of surrounding rock is rarely compared (Feng et al. 2015, 2019; Xue et al. 2020). In the present study, an MS monitoring system was established in the traffic tunnel of the tailrace surge chamber at the Shuangjiangkou hydropower station, Southwest China. Based on the characteristics of MS tempo-spatial activities induced by excavation unloading, the main damage areas of rock mass were delineated. Combined with field construction and geological conditions, the main factors resulting in rock mass damage were revealed. The source parameter characteristics of different MS clusters were analysed to investigate the damage evolution mechanism. Finally, a three-dimensional model was established and the stress and deformation characteristics of rock mass were compared with MS monitoring results. It was expected to provide technical support for the construction safety of the deep-buried tunnel of Shuangjiangkou Hydropower station and other similar tunnels.