Groundwater lowering for construction of the Kilsby Tunnel – pumping and tunnelling

The Kilsby Tunnel, constructed in the 1830s under the direction of Robert Stephenson, faced severe problems when a section of the tunnel, almost 400 m long, was driven through water-bearing unstable ‘quicksand’ conditions. Contemporary methods were not well suited to tunnelling through such conditions, and in previous decades, several canal tunnels had been planned to specifically divert around expected ‘bad ground’, and others took years to complete at great expense. Stephenson’s team, drawing on their experience from the mining industry, did not take this approach and ultimately worked through the unstable ground, albeit with considerable delays and cost increases. This was achieved in part by establishing a large-scale groundwater pumping system, unique for the time, that lowered groundwater levels and stabilised the quicksand, which resulted from a buried channel of glaciofluvial sands, cut into bedrock, that had been missed by trial borings. Steam engines were used to pump from multiple shafts (including four dedicated pumping shafts, off set from the tunnel alignment), with a reported pumping rate of 136 l/s for several months. One unusual feature was the use of flatrod systems to transmit mechanical power horizontally; this allowed a single engine to drive pumps in several different shafts.

Groundwater Lowering for Construction of the Kilsby Tunnel – Geological and Geotechnical Interpretation

The Kilsby Tunnel, constructed in the 1830s, faced severe problems when a section of the tunnel, almost 400 m long, encountered unstable ‘quicksand’ conditions. The engineer for the project, Robert Stephenson, developed an extensive groundwater lowering scheme, unique for the time, using steam engines pumping from multiple shafts, to overcome the quicksand. Modern geological information indicates most of the tunnel was in Middle Lias bedrock, but the ‘quicksand’ section passed through a buried channel of water-bearing sand of glacial origin. In the early 19th century the impact of glacial processes on British geology was not widely accepted and, based on contemporary geological knowledge, Stephenson’s problems appear to be genuine unforeseen ground conditions, not predicted by his experienced advisers. It seems just random chance that trial borings missed the buried channel of sand. The work at Kilsby was two decades before Darcy’s law established the theoretical understanding for groundwater flow, and 90 years before Terzaghi’s effective stress theory described how reducing pore water pressures changed ‘quicksand’ into a stable and workable material. Despite the lack of existing theories, Stephenson used careful observations and interpretation of groundwater flow in the ‘quicksand’ to navigate the tunnel project to a successful conclusion.

Enhanced Raman Spectra in Femtosecond Laser Inscribed Yb:YVO4 Channel Waveguides

The femtosecond laser writing with double-line technique was employed to fabricate buried channel waveguides with different widths in Yb:YVO4 crystal. Model profiles of the waveguides were captured using the endface coupling setup at the wavelength of 633 nm under TE and TM polarization. Furthermore, the confocal micro-Raman spectra in bulk and waveguide areas were studied at the wavelength of 633 nm. The enhanced Raman intensity were performed in waveguide areas.

Partial Isolation Type Buried Channel Array Transistor (Pi-BCAT) for a Sub-20 nm DRAM Cell Transistor

In this paper, we propose a new buried channel array transistor structure to solve the problem of current leakage occurring in the capacitors of dynamic random-access memory (DRAM) cells. This structure has a superior off current performance compared with three previous types of structures. In particular, the proposed buried channel array transistor has a 43% lower off current than the conventional asymmetric doping structure. Here, we show the range of the effective buried insulator parameter according to the depth of the buried gate, and we effectively show the range of improvement for the off current.

Ground penetrating radar inspection for Subsurface Historical Structures at Baptism (El-Maghtas) site, Jordan

The Baptism (El-Maghtas) site located north to the Dead Sea at the eastern bank of the Jordan River. There are many excavations in the surrounding area that revealed different archaeological remains which indicates the location John the Baptist. He lived and preached in the early 1st Century A.D. who is famous for John the Baptist baptized Jesus. The archaeological excavations reveal walls, antiquities, ancient water systems includes such conduits, pools, and ancient pottery pipes. The Ground Penetrating Radar (GPR) survey was carried out at selective locations along parallel profiles at the study using a Subsurface Interface Radar System (SIRvoyer-20) with either 400 MHz or 900 MHz mono-static shielded antennas manufactured by Geophysical Survey Systems Inc to delineate possible shallow archaeological material at shallow depth. The GPR radar-gram profiles revealed different subsurface anomalies across all sites. At John the Baptist Church site buried wall were detected along with profiles, the GPR survey recognized shallow wall and shallow buried channel at the pool's site. At Elijah's Hill site the GPR data confirmed the extension of an ancient pottery pipe. Basically the clear diffraction hyperbola anomaly related to the ancient pottery pipe could be discriminated from the 2D profiles. The GPR data was displaced using 3D imaging to define the horizontal and vertical extent of the pipe.