فهرس المقالات Strength reduction

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  1 - Soil-Interaction of Intake Pressure Tunnels under Ground Strength Reduction Conditions due to Cracking of the Lining(Case study: Dasht-e-Abbas intake pressure tunnel)
  seysd majddin Mir Mohammad Hosseini P Malek Mohammadib M. Asadolahi Pajouhc
  The induced cracks on the concrete lining of the intake pressure tunnels may cause the water seep into the surrounding media leading to develop a hydro pressure on the external surface of the lining. In the common design practice, the lining can be designed to tolerate أکثر

  The induced cracks on the concrete lining of the intake pressure tunnels may cause the water seep into the surrounding media leading to develop a hydro pressure on the external surface of the lining. In the common design practice, the lining can be designed to tolerate with this pressure using the Schleiss method. However, when the tunnel is constructed above the underground water, the seepage may cause the strength of the ground to reduce the amount of which may be considerable in some water sensible soils. In this paper, the finite element package of PLAXIS has been used to do the non-linear analysis of an intake pressure tunnel located inside a mudstone soil. The stress-strain model for the lining is taken linear elastic and for the soil is the elasto-plastic Mohre-Columb. The analysis is carried out by developing a 2D numerical model for an area of 100X73 meters. Consequently, the optimum lining is designed while the soil strength reduction occurs due to the seepage of water through the cracks in the lining. The results of numerical analysis are compared with that obtained from Schleiss common method of designing. Finally, a series of parametric studies are carried out and some important points and comments are suggested for designing of intake pressure tunnels facing the same condition. تفاصيل المقالة
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  2 - The Stability Assessment of Dasht-e-Abbas Pressure Intake Tunnel Subjected to Ground Strength Reduction-Iran
  S. M Mir Mohammad Hosseini P Malek Mohammadi M Kargar
  The hydraulic pressure is one of the most important factors in the design of pressure intake tunnels. Since the surrounding media cannot usually resist the high internal pressure of these tunnels, they are usually finished with an adequate lining mostly of reinforced co أکثر

  The hydraulic pressure is one of the most important factors in the design of pressure intake tunnels. Since the surrounding media cannot usually resist the high internal pressure of these tunnels, they are usually finished with an adequate lining mostly of reinforced concrete, which is an interaction problem between water, soil or rock and concrete lining. Although reinforcing the concrete lining may reduce the width and number of the developed cracks in the lining, the penetration of water into the surrounding media can still happen due to high water pressure in the tunnel. Thus, it may lead to the development of hydro pressure on the external surface of the lining. There are some theoretical methods that are developed for the design of tunnel lining in this condition. When the tunnel is located above the underground water table, the seeping water may lead to strength reduction of the adjacent soils, particularly when the ground, like the mudstone layers existing in Dasht-e-Abbas region, south-west of Iran, is cohesive and consists of soils that are susceptible to water. In this paper, the hydrostatic interaction between soil and concrete lining of Dasht-e-Abbas pressure intake tunnel has been investigated when the shear strength parameters of the mudstone layers decrease due to the seepage of water to the surrounding media. To evaluate the stability of the tunnel, a two dimensional numerical simulation is developed using the finite element code called PLAXIS and interaction analyses are carried out. The analyses are done in stages to assess the maximum internal forces induced in the lining. The structural stability of the tunnel is evaluated and discussed in this condition. Based on the obtained results, it is noted that for more realistic understanding of the behavior of infrastructures like pressure intake tunnels under various conditions, numerical analyses should also accompany experimental and analytical approaches such as Schleiss method which is described in this paper, especially for tunneling in media that is susceptible to water and ground strength reduction. The numerical analysis results show a considerable increase in the lining internal forces when subjected to the reduction of ground strength. However, the tunnel structure is still stable under the effect of surrounding ground degradation with the constructed lining specifications. تفاصيل المقالة