A review on the performance of the underground tunnels against blast loading

The tunneling system has become an important part of the present infrastructure system in all over the world. Therefore, it has become important to ensure the safety of the tunnels against any type of man-made blasting activities or other accidental blasting occurrence. In order to evaluate the performance of the tunnels against blast loading, a detailed review is carried out. Based on the review in the last couple of decades, the various parameters such as tunnel lining materials, tunnel shapes, tunnel lining thickness, tunnel burial depth, charge weight and standoff distance are high influences on the performance of underground tunnels against blast loading. It was observed that the tunnel roof and the tunnel wall center are most vulnerable to the blast loads. Also, it was found that more of the tunnel lining thickness results in lesser deformation at the tunnel roof and the tunnel wall center. The increase in the burial depth of the tunnel would reduce the extent of damage to the tunnel caused by effects of surface blast loading. The stiffness and strength of the ground media may be enhanced against the effects of blast loading by grouting measures. The studies revealed that the lining materials possessing blast waves absorbing properties can be best suited to be used in tunnel linings. Further, it was observed that more damage was caused to the tunnels due to the magnitude of the charge weight. An increase in the blast load causes a significant increase in the fracture area, residual stress and lateral displacement caused to the tunnel by the action of blast load. The standoff distance of the blast load from the tunnel also plays a significant role in the damage of the tunnel. More is the distance between the charge and the tunnel, lesser damage caused to the tunnels. In addition to that, the lining thickness was predicted and the trend was calibrated and fitted logarithmically with the available results. Based on the observation from the literature, it is concluded that the use of a single lining material in the tunnel against blast loading was studied predominantly in the couple of decades. Further, the performance of the tunnels in combination of different tunnel lining materials against blast loading was found limited. The influence of barriers to save the underground tunnels against blast loading was found limited.

High frequency atomic tunneling yields ultralow and glass-like thermal conductivity in chalcogenide single crystals

Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals. However, this behavior is rare, and its microscopic origin remains unclear. Here, we report the observation of ultralow and glass-like thermal conductivity in a hexagonal perovskite chalcogenide single crystal, BaTiS3, despite its highly symmetric and simple primitive cell. Elastic and inelastic scattering measurements reveal the quantum mechanical origin of this unusual trend. A two-level atomic tunneling system exists in a shallow double-well potential of the Ti atom and is of sufficiently high frequency to scatter heat-carrying phonons up to room temperature. While atomic tunneling has been invoked to explain the low-temperature thermal conductivity of solids for decades, our study establishes the presence of sub-THz frequency tunneling systems even in high-quality, electrically insulating single crystals, leading to anomalous transport properties well above cryogenic temperatures.

Automated Waste Transfer System using Dedicated Corridor in Cities

The Waste disposal techniques have become quite old for the modern period lately. The transfer of waste from the waste bins in the localities through the use of compactor trucks needs to be changed. It stands low on the efficiency scale. This can be improved by Channelizing waste through a separate corridor. The idea is to channelize the waste underground by using belt conveyor systems. The waste collector bins in the localities will be joined to the main conveyor heavy duty belts by small conveyor belts to move the waste. This waste will be taken to the waste processing plants by the belts fixed underground. The waste collector bins will be equipped with the pressure plates and will be connected to the network. As soon as the bin is full, it will send the information to the control centre. The operator at the centre can empty the bin by clicking a button. This will help to live monitor the waste and move it as soon as possible. The waste which is channelized can be easily segregated at the end where it enters the waste processing plant. Segregation of the waste will allow us to reuse the recyclable materials which most of the time are dumped in the landfills. The idea is to eliminate the Compactor Trucks as they cause pollution and congestion. Also many a times, waste materials are dropped out from the truck while carrying them to the processing plants which affects the riders behind it. The smoke from the trucks is dark and sooty which are the main causes for the lung diseases. Whereas the belt driven system will work on electricity. This energy can be harnessed by renewable energy resources or by power plants where the efficiency is the highest. The concept of underground tunneling in a well-planned layout is needed for laying of the sewer lines as they require heavy earth digging. Hence this underground waste transfer tunneling system can also be well established during the sewer line excavation work and can be implemented for the new smart cities which are going to be built. The efficient functioning of this system will save fuel, energy, time and creates an ecofriendly environment by cutting the carbon footprint.

The Analysis of the Stress-Strain State of the System “Equipment Complex - Support - Rock Mass” in the Bottomhole Area of the Shaft

The development of new deposits enterprises requires the construction of deep and super deep vertical shafts. The duration of their construction reaches 8 - 10 years with multi-billion capital investments. To reduce the payback period of these costs, it is necessary to develop and implement effective solutions to increase the speed of sinking operations through the wide introduction of brand-new mechanized equipment complexes. In response to the sinking in the bottomhole area of the shaft a complex, the following geotechnological system is being formed: "tunneling system - support - rock mass", the regularities of which require further study. For these purposes, an analytical method for calculating the shaft support can be used in the context of consideration of a planar contact problem at various phases of the system operation. The mutual coordination of individual phases in accordance with the classical concepts of the underground structures mechanics is possible with the help of a correction factor to the magnitude of horizontal stresses in the rock mass. In this paper we developed the algorithm which determines this coefficient, taking into account the influence of the main technological factors: the jack system pressure of the complex and the speed of sinking.