The Experts below are selected from a list of 117729 Experts worldwide ranked by ideXlab platform
Seisuke Okubo - One of the best experts on this subject based on the ideXlab platform.
-
some attempts for estimating rock strength and rock mass classification from cutting force and investigation of optimum operation of tunnel boring machines
Rock Mechanics and Rock Engineering, 2006Co-Authors: Katsunori Fukui, Seisuke OkuboAbstract:Tunnel face and wall collapse are common during Excavations performed by tunnel boring machines (TBMs) due to the difficulty of correctly identifying the properties of the excavated rock. This identification, however, can be simplified by using the cutting force to estimate rock strength, a method that has already proved quite successful in Japanese tunnel Excavations. This paper summarizes knowledge relating to the cutting force obtained through tunnel Excavation experience, and the relationship between rock strength and TBM operation is discussed. Although TBM operators rely on intuition to set the cutter head speed appropriately, this decision process represents a logical method of operation that takes advantage of the variable speed capability of the cutter head. Selection of appropriate support methods for the excavated face is also a critical issue in tunnel Excavation. This selection process is based on the condition of the rock, which is difficult to determine quickly and accurately during tunnel Excavation. The present paper uses the Excavation of two tunnels to demonstrate that it is possible to assign rock mass classifications accurately based on rock strength when boring a uniform rock type. It is also shown that the rock mass can be classified from the rock strength normalized by the uniaxial compressive strength when boring through mixed rock types.
Christian Moormann - One of the best experts on this subject based on the ideXlab platform.
-
analysis of wall and ground movements due to deep Excavations in soft soil based on a new worldwide database
Soils and Foundations, 2004Co-Authors: Christian MoormannAbstract:This study is based on an extensive database of more than 530 current international case histories on deep Excavations mostly in soft soils. The measured retaining wall and ground movements of all Excavations were analysed, taking into account the subsurface and groundwater conditions, the geometric boundary conditions as well as the support system and the Excavation method used in each case. By means of the database an empirical analysis of the behaviour of Excavation support systems is performed and the main factors affecting the behaviour of deep Excavations are examined. Special focus is set on identification of relationships between wall and ground movements, the support system employed and the Excavation method used. The results are compared with previous empirical studies.
Ellery Frahm - One of the best experts on this subject based on the ideXlab platform.
-
chemical soil surveys at the bremer site dakota county minnesota usa measuring phosphorous content of sediment by portable xrf and icp oes
Journal of Archaeological Science, 2016Co-Authors: Ellery Frahm, Gilliane F Monnie, Nicolas A Jelinski, Edward P Fleming, Ia L Arbe, Justice LamboAbstract:Abstract The Bremer Site lies along the shores of Spring Lake in southeastern Minnesota, and Excavations in the 1950s uncovered evidence of Woodland and Mississippian occupation phases. In 2011, a new program of systematic survey and Excavation began to better understand cultural patterning and diachronic changes at the Bremer Site. The investigations came to include microarcheaological methods, including sediment micromorphology and soil chemistry. No element has received more archaeological attention than P, which can reflect human and animal waste, organic refuse, burials, and ash. There has been interest in integrating soil chemistry into the workflow of fieldwork and in the potential of portable analytical instruments to yield data within the timeframe of an Excavation season. The last few years have seen the rise and proliferation of portable XRF (pXRF) instruments in archaeological studies. The newest generation of pXRF instruments is able to quantify P at low concentrations, and our focus here is developing effective methods to do so in archaeological soils and sediments. Using sediments from the Bremer Site, we evaluate two preparation techniques in order to find which one best balances analytical quality and preparation time. To analyze as many specimens as possible during an Excavation season, it is desirable to identify adequate preparation methods as well as the smallest number of analyses needed to attain reasonable confidence levels. Regarding repeatability, we show that, to attain P values with a standard error better than 10% or 20% of the mean, one or two analyses per specimen are sufficient in a majority of cases. Regarding reproducibility, we compare the pXRF data to two independent ICP-OES datasets. Ultimately, these tests aid in establishing methods that enable archaeologically significant pXRF analyses of soil P concentrations, even when working far from an analytical laboratory.
-
ten seconds in the field rapid armenian obsidian sourcing with portable xrf to inform Excavations and surveys
Journal of Archaeological Science, 2014Co-Authors: Ellery Frahm, Everly A Schmid, Oris Gasparya, Enik Yeritsya, Sergei Karapetia, Khachatu Meliksetia, Daniel S AdleAbstract:Armenia has one of the most obsidian-rich natural and cultural landscapes in the world, and the lithic assemblages of numerous Palaeolithic sites are predominantly, if not entirely, composed of obsidian. Recent Excavations at the Middle Palaeolithic cave of Lusakert 1 recovered, on average, 470 obsidian artifacts daily. After sourcing more than 1700 artifacts using portable XRF (pXRF) in our field house, our team sought to shift pXRF-based obsidian sourcing into the field itself, believing that the geological origins of artifacts would be useful information to have on-site during an Excavation or survey. Despite increasing use of portable instruments, previous studies have principally focused on collections in museums and other archives, and as a result, obsidian sourcing has remained embedded in post-Excavation studies. One critical factor in the uptake of obsidian sourcing in the field is the time needed to measure each artifact, frequently 2–6 min in previous studies. Here we report our two methods of obsidian sourcing, including source matching done automatically by the pXRF instrument's onboard software, in only 10 s. Our tests with Armenian geological specimens and Palaeolithic artifacts demonstrate the high efficacy of our two methods, which are sufficiently fast to become syncopated with our Excavation and survey activities. By reducing measurement times from a mode of 300 s in recent studies to just 10 s, here we show how (and why) to shift pXRF-based obsidian sourcing from the context of “white lab coats” to that of “muddy boots.”
Katsunori Fukui - One of the best experts on this subject based on the ideXlab platform.
-
some attempts for estimating rock strength and rock mass classification from cutting force and investigation of optimum operation of tunnel boring machines
Rock Mechanics and Rock Engineering, 2006Co-Authors: Katsunori Fukui, Seisuke OkuboAbstract:Tunnel face and wall collapse are common during Excavations performed by tunnel boring machines (TBMs) due to the difficulty of correctly identifying the properties of the excavated rock. This identification, however, can be simplified by using the cutting force to estimate rock strength, a method that has already proved quite successful in Japanese tunnel Excavations. This paper summarizes knowledge relating to the cutting force obtained through tunnel Excavation experience, and the relationship between rock strength and TBM operation is discussed. Although TBM operators rely on intuition to set the cutter head speed appropriately, this decision process represents a logical method of operation that takes advantage of the variable speed capability of the cutter head. Selection of appropriate support methods for the excavated face is also a critical issue in tunnel Excavation. This selection process is based on the condition of the rock, which is difficult to determine quickly and accurately during tunnel Excavation. The present paper uses the Excavation of two tunnels to demonstrate that it is possible to assign rock mass classifications accurately based on rock strength when boring a uniform rock type. It is also shown that the rock mass can be classified from the rock strength normalized by the uniaxial compressive strength when boring through mixed rock types.
Zhifa Yang - One of the best experts on this subject based on the ideXlab platform.
-
back analysis of long term stability of a 92 m span ancient quarrying cavern
Journal of rock mechanics and geotechnical engineering, 2017Co-Authors: Yanjun Shang, Lihui Li, Wantong He, Luqing Zhang, Tianbin Li, Zhifa YangAbstract:Abstract Long-term stability of large-span caverns is a challenging issue for design and construction of underground rock engineering. The Heidong cavern group consisting of 21 caverns was constructed about 1400 years ago for quarrying in massive Cretaceous tuff. The cavern No. 5 of the Heidong cavern group is characterized by an unsupported span up to 92 m, with the overburden thickness of only 3–25 m. To analyze its long-term stability, a detailed investigation was conducted to obtain its geometry and rock mass characteristics, and to monitor surrounding rock displacements. Based on field survey and laboratory tests, numerical simulations were performed using the finite difference code FLAC 3D . The analysis results revealed that for the long-term stability of the cavern No. 5, some major factors should be carefully considered, such as cavern Excavation method in hard massive rocks, site investigation using trial pits, tools like short iron chisel and hammer for manual Excavation, geometric dome roof, and waste rocks within abutment or on the floor. The highlights of the technologies obtained from this large-scale ancient underground project can provide reference for other similar project Excavations in practice.
