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    Effect of root water uptake on road movement across seasonal changes
    (2025-01-01)
    Yuliana, Yuliana
    ;
    Apriyono, Arwan
    ;
    Leung, Anthony Kwan
    ;
    Keawsawasvong, Suraparb
    ;
    Kamchoom, Viroon
    The use of trees as roadside barriers provides benefits like noise and pollution control. On the other hand, the root systems can disrupt soil moisture, leading to uneven subsidence and impacting nearby structures. Knowing the appropriate distance between trees and pavement will allow for maximizing the plant's favourable impact on infrastructure. This study aimed to determine the safe distance between trees and pavement by examining the effects of transpiration on pore water pressure (PWP) and pavement subsidence under seasonal variations. The root water uptake was simplified in a finite element model using multiple hydraulic head boundaries and validated through field observations. A hypoplastic model was employed to simulate the non-linear behaviour and plastic strain accumulation in unsaturated soil. The findings indicate that the summer season exhibited a more noticeable change in negative PWP. Trees significantly reduce PWP, especially during summer seasons, creating higher suction near them due to evapotranspiration. Additionally, pavement edges closest to trees experience the most pronounced subsidence, likely due to a greater soil moisture deficit. Seasonal variations influence subsidence, with drier periods leading to more severe effects. Furthermore, the pavement with the distance 4 meters from the tree highlights a potential risk exceeded the cracking moment at 5<sup>th</sup> summer period, indicating a high risk of damage.
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    Reconfirmation of Skempton-Bjerrum 2D to 3D settlement conversion using FEM of full scale embankments
    (2018-06-01)
    Chaiyaput, S.
    ;
    Bergado, D. T.
    The soil is a production of natural process, which is highly variable with very complex properties, and soil behavior can be difficult to calculate. Numerical Simulation can be applied to deal with the numerous aspects of complex geotechnical structures. The 3D FEM simulation model can present the conditions of the geotechnical project in details and assumptions, which are similar to actual situations, but the process of running the 3D FEM analysis takes longer computer time. Therefore, 2D FEM simulation model is proposed to reduce calculation time, but the prediction results are usually overestimated. Accordingly, this paper re-analyzed the 2D analysis to represent the performance of 3D analysis based on Skempton-Bjerrum method. The simulated 2D and 3D FEM settlement results had been carried out and compared with the measured data of two full scale embankments including the dissipation of the excess pore pressure. Consequently, it was confirmed that predicted result of 2D and 3D FEM numerical simulation agreed with the correction of Skempton-Bjerrum method that can be applied to predict the final settlements in 3D conditions.
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    Describing settlement troughs over twin tunnels using a superposition technique
    (2007-04-01)
    Suwansawat, Suchatvee
    ;
    Einstein, Herbert H.
    It has been observed in many tunneling projects that surface settlement troughs caused by twin tunnels have a variety of shapes unlike single tunnels, where symmetric surface settlement troughs are usually observed. The surface settlement troughs observed over twin tunnels can be symmetric with respect to the midpoint between the two tunnels or symmetric but shifted toward either side or they can also be asymmetric. Settlement troughs both over single and twin tunnels (when symmetric) can often be described by a Gaussian curve. Most of the cases reported in the literature do consider the effect of ground conditions, tunnel size, and depth on the surface settlement. However, these cases do not consider the effect of construction operation. A study of settlements above tunnels driven with earth pressure balance shields in Bangkok made it possible to include operational parameters such as face pressure, penetration rate, and grouting pressure. This is possible by comparing the effect of twin tunnels which are geometrically and geologically identical but differ in the operational characteristics. These operational differences make it, however, more difficult to describe the resulting settlement troughs over twin tunnels using existing methods. Therefore, this paper introduces a superposition technique to describe surface settlement troughs over twin tunnels. It appears that one can construct settlement curves induced by the first shield and the second shield using the Gaussian function and combine the curves to obtain a total settlement trough as a result of the twin tunnels. Using extensive data from the Bangkok Subway Tunnel project, this approach was found to be suitable both for twin tunnels excavated side-by-side and also for stacked twin tunnels. Right now this superposition technique is basically descriptive. Eventually it will be possible to use this approach to predict settlement troughs over twin tunnels. © ASCE.