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The development and in-situ use of fiber optic continuous strain monitoring for tunnel support elements
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2020
A rising demand for underground transportation and resource management has led to the development of many more subterranean projects (deep foundations, tunnels, utility corridors etc.) which are constructed at larger scales, over greater distances, increased depths, and within proximity to sensitive urban environments (i.e. reduced tolerances with respect to adjacent infrastructure). For such projects, engineering design of support is primarily based on the stress and strain that are developing within the support structures as a result of the surrounding ground conditions. These ground loads are distributed continuously and spatially and as such, an improved understanding of the continuous strain profile would provide better insight into the true behaviour of such support elements. Research currently being conducted at the Royal Military College of Canada and Queen’s University focuses on such micro-scale geomechanical mechanisms and interactions with a view to determining the overall design implications for full-scale support design for tunnels. The use of fiber optics within the Geotechnical/Geological Engineering field is not a new concept. There are multiple projects that have utilized a particular type of fiber optic technology in the past, ranging from their use to monitor the construction and performance of embankments, tunnels, piles, mining operations and other geotechnical works. It is important to note that not all fiber optic technologies are similar as each type has their unique strengths and limitations. Historically, monitoring of such ground support members has been limited to electrical and mechanical techniques (e.g. foil-resistive strain gauges, inclinometers, linear variable displacement transducers). Such techniques provide discrete measurement points, implying that many sensors are required to obtain a full strain profile along the length of the support element (Vlachopoulos and Forbes, 2018).
The development and in-situ use of fiber optic continuous strain monitoring for tunnel support elements
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2019
A rising demand for underground transportation and resource management has led to the development of many more subterranean projects (deep foundations, tunnels, utility corridors etc.) which are constructed at larger scales, over greater distances, increased depths, and within proximity to sensitive urban environments (i.e. reduced tolerances with respect to adjacent infrastructure). For such projects, engineering design of support is primarily based on the stress and strain that are developing within the support structures as a result of the surrounding ground conditions. These ground loads are distributed continuously and spatially and as such, an improved understanding of the continuous strain profile would provide better insight into the true behaviour of such support elements. Research currently being conducted at the Royal Military College of Canada and Queen’s University focuses on such micro-scale geomechanical mechanisms and interactions with a view to determining the overall design implications for full-scale support design for tunnels. The use of fiber optics within the Geotechnical/Geological Engineering field is not a new concept. There are multiple projects that have utilized a particular type of fiber optic technology in the past, ranging from their use to monitor the construction and performance of embankments, tunnels, piles, mining operations and other geotechnical works. It is important to note that not all fiber optic technologies are similar as each type has their unique strengths and limitations. Historically, monitoring of such ground support members has been limited to electrical and mechanical techniques (e.g. foil-resistive strain gauges, inclinometers, linear variable displacement transducers). Such techniques provide discrete measurement points, implying that many sensors are required to obtain a full strain profile along the length of the support element (Vlachopoulos and Forbes, 2018).
Statistical assessment of groundwater quality using hydrochemical parameters for drinking water of rural areas in Nashik district, Maharashtra, India
Published in Water Science, 2022
C.A. Patil, P.M. Nalawade, B. L. Gadakh, N.V. Khangar
The area of the Nashik district is underlain by the elementary lava flows of top Cretaceous to lower the Eocene epoch. The shallow alluvial formation of recent age also occurs as a narrow stretch along the banks of the Godavari, Mosam, and Girna River flowing in Nashik. Basaltic lava flows occupy about 85% of the area of the district. These flows are normally horizontally disposed over a wide stretch and give rise to tableland type of topography also known a plateau. These flows occur in layered sequences and are represented by a massive unit at the bottom and a vesicular unit at the top of the flow. These flows are separated from each other by a marker bed known as ‘bole bed.’ The groundwater in Deccan Trap Basalt occurs mostly in the upper weathered and fractured parts down to 20–25 m depth. At places, potential zones are encountered at deeper levels in the form of fractures and inter-flow zones. The top weathered and fractured parts form subterranean aquifer and groundwater occurs under water table (unconfined) conditions. At more limitless levels, the groundwater occurs under semi-confined to confined conditions.
Quaternary uplift and fault movement near Waitomo, North Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Faulting provides fracture zones that are exploited by subterranean karst streams, and the passages in Ruakuri Cave can be seen to be oriented along a geometrical pattern of intersecting joints (Figure 6). These passages were formed by the Okohua Stream that emerges at the foot of a 50 m cliff just prior to joining the Waitomo Stream (Figures 5 and 6).
Investigation on immiscible N2 WAG and SWAG after water flooding in the paleo-subterranean river of fractured-vuggy reservoirs
Published in Petroleum Science and Technology, 2023
Wanjiang Guo, Xiaofei Li, Aifen Li
The following conclusions can be drawn from the experimental results and simulations: Much remaining oil exits in paleo-subterranean river karst reservoirs after water flooding. Moreover, the occurrence locations and types of these remaining oil are different, i.e., shielded remaining oil, attic remaining oil, corner remaining oil, and blind end remaining oil. Gravity segregation of water and oil, resistance differentiation, and well placement are the main reasons for remaining oil formation.WAG can extract the shielded remaining oil, attic remaining oil, and part of corner remaining oil efficiently, while SWAG can only work on attic remaining oil. The smaller gas-oil capillary force causes the extraction of shielded remaining oil; the gravity segregation between gas and oil is the critical factor in the recovery of attic remaining oil; the driving effect of gas on the water can enlarge the swept zone of water, and thus extract part of the corner remaining oil.WAG and SWAG can continue to increase oil production after water flooding failure. However, compared with the SWAG, the oil production time of WAG after water flooding is more prolonged, and the ultimate recovery ratio is higher. The oil production rate curve during WAG is like a wavy line, which during SWAG decreases gradually after the initial increase.Injection rate, gas-water ratio, and slug size are the key parameters affecting the recovery ratio during WAG and SAWG. Suppose the values of these parameters are too high, it is easy to cause gas channeling and affect the improvement of recovery. However, too low injection rate lacks driving force support, affecting the expansion of the swept zone; too small gas-water ratio and slug size can’t play a good role in gas displacement. The optimal injection rate, gas-water ratio during SWAG, and the slug size during WAG in the paleo-subterranean river karst reservoirs are 1.5mL/min, 0.25, and 0.3PV, respectively.