scholarly journals Optimization Effects of Load Reduction for Earth Pressure on High-Filled Cut-and-Cover Tunnels Using the Discrete Element Method

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Bentian Yu ◽  
Junying Xia ◽  
Sheng Li ◽  
Liangliang Zhao
Keyword(s):  
Discrete Element Method ◽  
Cross Section ◽  
Earth Pressure ◽  
Discrete Element ◽  
Expanded Polystyrene ◽  
Influential Factors ◽  
Northwestern Part ◽  
Load Reduction ◽  
Section Type ◽  
Element Method

In the Northwestern part of Loess Plateau of China, the ravine and valley are numerous; therefore, high-filled cut-and-cover tunnels (HFCCTs) play a major role in meeting traffic needs and creating a great deal of usable land. However, due to higher backfill soil, a high earth pressure is generated, which affects the safety of HFCCTs. To this end, using the discrete element method (DEM), three load reduction measures were introduced to evaluate HFCCT: the cross section types of HFCCT; the combination of optimized cross section type with load reduction using expanded polystyrene (EPS); and the combination of optimized cross section type with load reduction using the EPS and concrete wedge (CW). We evaluated changes in earth pressure of HFCCTs with reference to the density and laying position of EPS and the height as well as width of CW. Parametric DEM studies were performed to characterize these influential factors. It was found that different cross section types of HFCCT have a certain influence on earth pressure distribution, and load reduction effects of EPS were extremely obvious, resulting in a sharp drop in vertical earth pressure on top of HFCCT and a slight growth in lateral earth pressure on the sides of HFCCT. Moreover, installation of CWs reduced the VEP and LEP of HFCCT. These factors were also shown to exert important effects on load reduction mechanisms of HFCCT. Based on their influence on earth pressure of HFCCT from a macroscopic and microscopic view, optimal values for influential factors were derived.

scholarly journals Influence of Structural Shape on Earth Pressure for High-Filled Cut-and-Cover Tunnel with and without Load Reduction Based on Discrete Element Method

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Sheng Li ◽  
Liangliang Zhao ◽  
I-Hsuan Ho ◽  
Guixia Ning ◽  
Bentian Yu ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Load Transfer ◽  
Earth Pressure ◽  
Vertical Displacement ◽  
Discrete Element ◽  
Expanded Polystyrene ◽  
Load Reduction ◽  
Structural Shape ◽  
Lining Structure ◽  
Element Method

In the construction of the Loess Plateau in China, high-filled cut-and-cover tunnels (HFCCTs) had solved the problem of the shortage of land resources. However, this type of structure has a large amount of backfill soil, which leads to the problems of ultrahigh earth pressure and safety of the cut-and-cover tunnels (CCTs) lining structure. Previous studies have focused on the load reduction of various flexible materials, ignoring the influence produced by the shape of the CCT structure on the load reduction. Therefore, via a discrete element software, we investigated the changes of vertical earth pressure (VEP), vertical displacement, lateral earth pressure (LEP), and load transfer mechanisms around a HFCCT with consideration to two cases: (1) different shape of CCT structure; (2) the coupling of load reduction using expanded polystyrene (EPS) and the modified shape of the CCT lining structure. The results obtained by the discrete element method (DEM) revealed that an appropriate structural shape influenced the reduction of the VEP above the CCT and that the coupled effects of the load reduction using the EPS and shape modifications of the CCT lining structure could significantly reduce the VEP above the CCT, which enhanced the safety of the CCT. Meanwhile, the optimal values for the shapes of CCTs are derived.

Load reduction on high-filled cut-and-cover tunnel using discrete element method

2019 ◽  
Vol 114 ◽  
pp. 103149 ◽  
Author(s):  
Sheng Li ◽  
I-Hsuan Ho ◽  
Li Ma ◽  
Yuxiang Yao ◽  
Changdan Wang
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Load Reduction ◽  
Element Method

Analysis of Time-Dependent Soil Behavior above High-Filled Cut-and-Cover Tunnels Using Discrete Element Method

2021 ◽  
Author(s):  
Sheng Li ◽  
Guoqiang Han ◽  
I-HSUAN HO ◽  
Li Ma ◽  
Balasingam Muhunthan ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Load Transfer ◽  
Earth Pressure ◽  
Vertical Displacement ◽  
Discrete Element ◽  
Time Dependent ◽  
Structural Safety ◽  
Dependent Behavior ◽  
Element Method

Abstract In the Northwest Loess Plateau of China that is full of mountains and deep valleys, high-filled cut-and-cover tunnels (HFCCTs) not only satisfy transportation demands, but they create usable land as well. Several studies have been conducted to investigate the feasibility of HFCCTs, but the time-dependent behavior of the significant backfill needed for HFCCTs has not been adequately examined. Settlement can be severely underestimated due to the time-dependent behavior of ultra-high backfill, and the earth pressure becomes redistributed accordingly. Therefore, the ability to predict the long-term behavior of backfill on HFCCTs is necessary to ensure the long-term safety of the structure. Using a discrete element method (DEM), the changes in vertical earth pressure (VEP), vertical displacement, and load transfer mechanisms above an HFCCT were investigated in this study under scenarios with and without considering backfill creep. The results show that the differential displacement of the soil and the surface settlement obviously increase due to creep and the subsequent cycles of primary and secondary consolidation. Moreover, the stress surrounding the HFCCT is redistributed, causing both the stress concentration and slope effect to weaken over time, but the VEP increases significantly. The micromechanical parameters also change correspondingly. Our results clearly show that the creep of high backfill soil must be considered carefully in HFCCT projects to ensure structural safety.

Discrete element method to model cracking for two layer systems

TAPPI Journal ◽  
2019 ◽  
Vol 18 (2) ◽  
pp. 101-108
Author(s):  
Daniel Varney ◽  
Douglas Bousfield
Keyword(s):  
Discrete Element Method ◽  
Flexural Modulus ◽  
Single Layer ◽  
Discrete Element ◽  
Flexural Stress ◽  
Layer System ◽  
Three Point Bending ◽  
Moving Force ◽  
Coating Layers ◽  
Element Method

Cracking at the fold is a serious issue for many grades of coated paper and coated board. Some recent work has suggested methods to minimize this problem by using two or more coating layers of different properties. A discrete element method (DEM) has been used to model deformation events for single layer coating systems such as in-plain and out-of-plain tension, three-point bending, and a novel moving force picking simulation, but nothing has been reported related to multiple coating layers. In this paper, a DEM model has been expanded to predict the three-point bending response of a two-layer system. The main factors evaluated include the use of different binder systems in each layer and the ratio of the bottom and top layer weights. As in the past, the properties of the binder and the binder concentration are input parameters. The model can predict crack formation that is a function of these two sets of factors. In addition, the model can predict the flexural modulus, the maximum flexural stress, and the strain-at-failure. The predictions are qualitatively compared with experimental results reported in the literature.

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