Papers by Keyword: Tunnelling

Abstract: The Q-system, developed by Barton et al. (1974), is a widely used rock mass classification system that provides a quantitative measure of rock mass quality. The Q-value, which ranges from 0.001 to 1000, is calculated based on six parameters: rock quality designation (RQD), joint set number (Jn), joint roughness number (Jr), joint alteration number (Ja), joint water reduction factor (Jw), and stress reduction factor (SRF). These parameters collectively capture the rock mass's geological and geotechnical characteristics, enabling a comprehensive assessment of its stability.The Q-value serves as a reliable indicator of rock mass quality, allowing engineers to predict potential stability issues and design appropriate support systems. A higher Q-value indicates better rock mass quality, while a lower Q-value suggests poorer quality and increased support requirements. By using the Q-system, engineers can optimize tunnel design and construction, reducing the risk of instability and associated costs.The predictive model developed in this study further enhances the utility of the Q-system by enabling the estimation of Q-values based on shale properties which allows engineers to anticipate rock mass behaviour and design support systems, accordingly, streamlining the tunnel construction process. The model's accuracy and reliability make it a valuable tool for tunnel designers and engineers working in weak shale formations. By leveraging the Q-system and predictive model, engineers can improve tunnel stability, reduce construction costs, and enhance overall safety.

Abstract: In this paper we report temperature independent near-interface traps (NITs) in the gate oxide of N-type MOS capacitors. The measurements were performed by a recently developed direct-measurement technique, which detected NITs with energy levels between 0.13 eV to 0.23 eV above the bottom of conduction band. These traps are also spatially localized close to the SiC surface, as evidenced by the fact that they are not observed at measurement frequencies below 6 MHz. The temperature independence indicates that this localized defect is different from the usually observed NITs whose density is increased by temperature-bias stress.

Abstract: Aiming at the problems in construction for a shallow-buried and unsymmetrical loading portal in Banzhulin Tunnel in Yu-Xiang expressway, the finite element simulation were carried on to study the behavior for bench excavation method. Main results of numerical analysis as follows:the displacement of surrounding rock of right tunnel(as AR)at the horizontal direction is large and may larger than that of the left tunnel(as AL) at the vertical direction,and the largest deformation is 22.63mm,occuring at the key point DL. Compared with the data of monitoring measurement, the correctness of this simulation was proved.The behavior for deformation and stress of mountain tunnels as Banzhulin is basically mastered,and the displacement of rockmass is the key factor in tunnelling.

Abstract: The sixth line of Guangzhou Metro Subway is partially located in silty fine sand layer, which is incompact, rich in water, and has high permeability and low bearing capability. When tunnelling in this section, it is easy to bring about gush of water and sand, which will cause the ground surface to settle. Therefore, a two-staged helical conveyer was used to control this phenomenon during tunnelling. First, both the dregs outlets of helical conveyer are turned off to prevent water and sand from rushing forth, then foam material is injected into the earth cabin and the front-end of helical conveyer to keep the cabin pressure from decreasing. Secondly, drain outlet of the second helical conveyer is turned on and the water is drained, then dregs outlet of the second helical conveyer is turned on to discharge the dregs. Finally, dregs outlet of the first helical conveyer is turned on to discharge the dregs in the earth cabin. Such technique was used successfully in tunnelling the section from Datansha to Ruyifang of the sixth line of Guangzhou Metro Subway. It ensured that sinking of the ground surface was avoided while the tunnel shield went through the silty fine sand layer that is rich in water.

Abstract: We study the sweep speed dependence of electron injection voltage in Si-Nano-Dots (Si-NDs) floating gate MOS Capacitor by using our collective tunneling model, which models the tunneling between two-dimensional electron gas (2DEG) and the Si-NDs. We clarify the sweep speed dependence of electron injection energy with a numerical calculation based on our collective tunneling model, that we developed to emulate the experiment in this system, and obtained a new insight into the origin of sweep speed dependence. We revealed that our model can reproduce the sweep speed dependence of electron tunneling. This insight is useful for designing future nano-electronic devices.

Abstract: The architectural heritage is subjected to various risk factors like the lack of maintenance, the material decay and the external solicitations. Nowadays, due to the ever-increasing demand for urban space, a relevant cause of structural damage that the historical buildings experience is the ground settlement due to excavation works. In the city of Amsterdam, for example, the construction of the new North-South metro line will involve an area characterized by the presence of many ancient masonry buildings. A fundamental phase of the design of this kind of projects is the assessment of the risk of subsidence which can affect the existing structures. The actual method to perform this assessment provides for a preliminary screening of the buildings located in the area surrounding the excavation, in order to evaluate which structures are at risk of settlement induced damage. It is based on the simplification of the building as a linear elastic beam and the assumption of the absence of interaction between the soil and the structure. An improved classification system should take into account the main parameters which influence the structural response, like the nonlinear behaviour of the building and the role played by the foundation in the soil-structure interaction. In this paper, the effect on the damage mechanism of the excavation advance and the location of the tunnel with respect to the building is evaluated. Numerical analyses are performed in order to understand the effect of different settlement profiles of the ground. A coupled model of the structure and the soil is evaluated, taking into account a damage model for the masonry building and the nonlinear behaviour of the soil-structure interaction. This paper demonstrates the importance of 3D modelling; neglecting the tunnel advance can lead to an underestimation of the damage.