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The utility tunnels used for electricity transmission are in high demand these days. The literature presents many limitations in the currently used cutterhead drive design procedure while using a shield tunnel boring machine (TBM) for the excavation of these relatively small diameter tunnels. In order to develop an appropriate design method specially for cutterhead drive, experimental data obtained through the operation of a 3560 mm diameter shield TBM were used in this research work. For experimental purpose, an earth pressure balance (EPB) shield TBM was manufactured and a facility was established for performing the full-scale tunneling tests. Numerous tests were performed through the variation of TBM operational parameters such as thrust force and the rotational speed of the cutterhead at four UCS (Uniaxial compressive strength) levels of artificial rock mass. The relationships between thrust force and torque were mainly established and the effects of UCS and rotational speed of cutterhead on these relationships are analyzed through a representative case of 100 MPa UCS. A novel torque estimation method is also presented in this study which can be conveniently used in the cutterhead drive design while using small diameter shield TBMs.

The demand for a net protection system for mitigating debris flow has increased recently for which new energy absorption devices have been hereby developed. The purpose of this study is to analyze the behavior and energy absorption rate of a brake frame, to find an efficient approach for its numerical simulation, and to increase its field applicability by analyzing its effects. Three methodologies were used for this purpose. Firstly, quasi-static load tests were conducted for analyzing the behavior of the brake frame. Secondly, three-dimensional FE modeling was performed to analyze the buckling and fractural behavior of steel rings. Lastly, the effects of the brake frame were numerically analyzed based on a proposed equivalent model. The results show that the brake frame can withstand the external force by elastic/local buckling, fracture of a steel ring, and elastic/plastic behavior of wire rope, and has the energy absorption rate of 53 kJ. It is deduced that the proposed equivalent model is capable to accurately simulate the behavior of the brake frame and can replace the three-dimensional model. The tensile force reduction in the system by using brake frames was observed to be about 75%. It is concluded that the proposed equivalent model for brake frame design is practically applicable.

There are two primary causes of the ground movement due to tunnelling in urban areas; firstly the lost ground and secondly the groundwater depression during construction. The groundwater depression was usually not considered as a cause of settlement in previous research works. The main purpose of this study is to analyze the combined effect of these two phenomena on the transverse settlement trough. Centrifuge model tests and numerical analysis were primarily selected as the methodology. The characteristics of settlement trough were analyzed by performing centrifuge model tests where acceleration reached up to 80g condition. Two different types of tunnel models of 180 mm diameter were prepared in order to match the prototype of a large tunnel of 14.4 m diameter. A volume loss model was made to simulate the excavation procedure at different volume loss and a drainage tunnel model was made to simulate the reduction in pore pressure distribution. Numerical analysis was performed using FLAC 2D program in order to analyze the effects of various groundwater depression values on the settlement trough. Unconfined fluid flow condition was selected to develop the phreatic surface and groundwater level on the surface. The settlement troughs obtained in the results were investigated according to the combined effect of excavation and groundwater depression. Subsequently, a new curve is suggested to consider elastic settlement in the modified Gaussian curve. The results show that the effects of groundwater depression are considerable as the settlement trough gets deeper and wider compared to the trough obtained only due to excavation. The relationships of maximum settlement and infection point with the reduced pore pressure at tunnel centerline are also suggested. [ABSTRACT FROM AUTHOR]