جستجوی مقالات مرتبط با کلیدواژه "فشار سینه کار" در نشریات گروه "عمران"

In urban environments, due to the existence of structures in the city such as buildings and, more importantly, the presence of people in them, as well as existing underground structures such as service spaces including sewage tunnels, aqueducts, and adjacent tunnels, there have been always concerned about damages to these structures and their interactions existed as a result of tunneling. Significant interaction effects can occur when a new tunnel is dug in the vicinity of an existing tunnel. For example, the construction of a new tunnel could impose unauthorized deformations or bending moments on the existing structural support system. This interaction depends on parameters such as the distance of the tunnels, the size of both tunnels, the rigidity of the support system and the method used to locate the second tunnel, and the geotechnical characteristics of the excavation site.Aqueducts are underground structures and excavating new tunnels can have special interaction effects on these structures. An aqueduct is a subterranean canal with a gentle slope, which connects water-rich zones at high altitudes to the fields where cultivation takes place.According to studies, the interaction between underground structures is one of the critical factors that affect ground displacement and subsidence. The effect of the interaction between the tunnels as well as the amount of face pressure on the ground subsidence has been investigated using methods such as physical modelling, numerical modelling, and local measurements. In this paper, the effect of face pressure has been investigated in excavating the 2nd tunnel Line of Tabriz Metro on existing aqueducts. It is worth noting that for 3D modelling, FLAC3D software is used in this paper.

In recent years, along with the development and expansion of cities, population growth and vehicles, the construction of underground railways by mechanized tunneling is increasing. One of the common problems of EPB-TBM mechanized tunneling in weak and unstable areas is tunnel convergence, which causes problems such as getting stuck on EPB-TBM, subsidence and damage to buildings around the tunnel in urban areas. Due to the uncertainty in the soil parameters of the region, estimating the face pressure, thrust jacks pressure and cutter head torque at different kilometers is very important to prevent over-convergence of the tunnel, getting stuck on EPB-TBM and ground subsidence. Due to the uncertainty in rock and soil, in this paper the amount of face pressure, thrust jacks force, cutter head torque and ground subsidence due to tunneling in different kilometers in the construction project of the new Istanbul airport in Turkey using numerical software, PLAXIS3D 2020, is modeled. The modeling results show that the operator can increase the face pressure by preventing getting stuck on EPB-TBM. According to the results obtained in this paper, adjusting the face pressure, thrust jacks force and cutter head torque, in addition to solving the problem of getting stuck on EPB-TBM, will reduce ground subsidence and damage structures on the ground surface.

In urban areas, tunneling is accompanied by ground surface settlement. To reduce the risks of the operation, it is always required to have an assessment of ground surface settlement and face pressure. In the evaluation of the face pressure, there are two major sets of methods based on the ultimate limit state (ULS) (e.g. tunnel face failure), and serviceability limit state (SLS) (e.g. unacceptable settlement or heave). In a serviceability limit state, volume loss and surface settlement are used for the analysis of the face pressure. The methods developed for the analysis of SLS face pressure are based on the results of small-scale centrifuge tests or case studies with the unpressurized face. Hence, realistic face pressure cannot be evaluated with these methods. This paper summarizes the major strategies for the evaluation of face pressure in an undrained condition. The outlined methods are utilized to evaluate tunnel face pressure in the Tehran metro line 6, south extension (ML6-SE) project. Results of the analyses showed that predicted face pressures with the SLS methods are far above the required face pressure. To make realistic SLS face pressure evaluations in this project (considering a maximum allowable surface settlement of 10 mm), using ground characteristics and TBM operational parameters, a new formula was introduced with a coefficient of determination of 84%. The results of this paper can be very helpful for both the design phase of a tunneling project and the construction period to adjust the face pressure based on the requirement of the allowable surface settlement.

In this study, the effect of some of the most important operational parameters of the tunnel boring machine (EPBM) has been investigated at the time of the tunnel excavation on the ground deformation and surface subsidence. The basis of this research is the finite difference method (FDM) using FLAC3D software. The numerical model was first constructed based on geotechnical parameters (physical and mechanical characteristics) of the Tehran Subway Southern Extension Tunnel-Line 6 and then calibrated and verified based on the "invisible tunnel" method. The results showed that by decreasing the boundary pressure on the face and the annulus, there is no significant change in the increase in the level of the surface subsidence. Also, the results of parametric analysis of the injection pressure of the grout showed that applying the pressure of the grout equivalent to the vertical geostatic stress relative to the horizontal geostatic stress in the tunnel face has more effect on the control of surface deformation and subsidence.