scholarly journals Model Tests of Earth Pressure on Buried Rigid Pipes and Flexible Pipes underneath Expanded Polystyrene (EPS)

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Qiang Ma ◽  
Zhun Ku ◽  
Henglin Xiao
Keyword(s):  
Earth Pressure ◽  
Model Tests ◽  
Expanded Polystyrene ◽  
Load Reduction ◽  
Flexible Pipe ◽  
Buried Pipe ◽  
The Earth ◽  
Flexible Pipes ◽  
Optimal Load ◽  
Reduction Efficiency

To obtain the optimal load-reduction scheme and calculation method of earth pressure on the crown of the pipe, the load-reduction efficiency of rigid pipe and flexible pipe with different thicknesses and layers of expanded polystyrene (EPS) is investigated by model tests, and the law of load reduction is obtained by analyzing the earth pressure and the displacements of the filling around the pipe. The test results show that the earth pressure is obviously reduced with EPS laying on the crown of pipe, and the load-reduction efficiency is increased to be constant with increasing of EPS thickness. In the case that the summation thickness of EPS is constant, the load-reduction efficiency of EPS with two layers spread on the pipe is higher than that of one layer only. Compared with the rigid pipe, the load-reducing effect of flexible pipe is more significant. Based on the data obtained from the model tests, the nonlinear earth pressure calculation formula obtained from regression analysis is adopted, and the results from it are compared with the existing formula consequences of the earth pressure on the buried pipe. The results show that the earth pressure calculated by nonlinear earth pressure theory is on the brink of that tested in the field. The research results can provide references for selection of load-reduction measures and calculation of earth pressure on the crown of the pipe.

scholarly journals Experimental Simulation for Load Reduction Techniques on Underground Utilities using Geofoam

2019 ◽  
Vol 2 (4) ◽  
pp. 372
Author(s):  
Bahr M. A. ◽  
Tarek M. F. ◽  
Hassan A, A. ◽  
Hassaan D. M.
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Expanded Polystyrene ◽  
Experimental Simulation ◽  
Flexible Pipe ◽  
Buried Pipe ◽  
Eps Geofoam ◽  
Reduction Techniques ◽  
Flexible Pipes ◽  
Series Of Experiments

This paper investigates an experimental study on reducing stress acting on buried flexible pipes by using expanded polystyrene (EPS) geofoam techniques. An experimental model was carried out with dimensions depending on pipe diameter (D) and location, the used fill cover material was from sand and EPS blocks either embankment form, or within sand backfill as embedded layer. The pipe flexible is un-plasticized polyvinyl chloride (UPVC). A series of experiments have been carried out by using static surface loading on rectangular steel plate,where the load is distributed over the backfill. The behavior of sand backfill around the pipe was observed, and the displacement and strains of the pipe were measured. The experimental results showed that the embedded layer of EPS geofoam block embedded in sand for different techniques reduced the deformation of flexible buried pipe, with high efficiency and low coast compared with EPS geofoam only. The results reveal that, the most effective methods thatcanreduce the stress on buried flexible pipe with low cost were EPS encasement block with head void method, and EPS block embraces the upper part of pipe method.

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.

Numerical Analysis of Slab Culvert Beneath Imperfect Ditch Covered with Geogrid Layers

2011 ◽  
Vol 71-78 ◽  
pp. 3338-3341 ◽  
Author(s):  
Jun Jie Zheng ◽  
De Pi Luo ◽  
Qiang Ma
Keyword(s):  
Numerical Analysis ◽  
Slope Angle ◽  
Earth Pressure ◽  
Numerical Analyses ◽  
Load Reduction ◽  
Earth Pressures ◽  
Reduction Efficiency ◽  
Reduction Effect ◽  
Vertical Earth Pressure

The overburden of high embankment culvert is over 10 m, such high fill always leads large earth pressure on the slab of the culvert. The imperfect ditch covered with geogrid method was employed to reduce the vertical earth pressure on the slab. A series of numerical analyses were performed to investigate the load reduction effect of the imperfect ditch. In the simulation, the number of geogrid layers, the geometry of the load reduction ditches, as well as the location and the stiffness of the geogrid are investigated to analyse the influences on the vertical earth pressures. The results show that the slope angle and the height of the ditch, the plane stiffness of the geogrid have great effect on the load reduction efficiency, ditches with higher height and a slope of 90°lead to a significantly reduction on vertical earth pressures on the crown of culverts. The width of load reduction ditch, number of geogrid layers, the location and spacing of the geogrids have little effect on load reduction, the results can provide references for load reduction of slab culvert.

Coordinated optimization control of shield machine based on dynamic fuzzy neural network direct inverse control

2020 ◽  
pp. 014233122098027
Author(s):  
Xuanyu Liu ◽  
Wentao Wang ◽  
Yudong Wang ◽  
Cheng Shao ◽  
Qiumei Cong
Keyword(s):  
Fuzzy Neural Network ◽  
Control Method ◽  
Earth Pressure ◽  
Screw Conveyor ◽  
Inverse Control ◽  
The Earth ◽  
Coordinated Optimization ◽  
Optimization Control ◽  
Fuzzy Neural ◽  
Shield Machine

During shield machine tunneling, the earth pressure in the sealed cabin must be kept balanced to ensure construction safety. As there is a strong nonlinear coupling relationship among the tunneling parameters, it is difficult to control the balance between the amount of soil entered and the amount discharged in the sealed cabin. So, the control effect of excavation face stability is poor. For this purpose, a coordinated optimization control method of shield machine based on dynamic fuzzy neural network (D-FNN) direct inverse control is proposed. The cutter head torque, advance speed, thrust, screw conveyor speed and earth pressure difference in the sealed cabin are selected as inputs, and the D-FNN control model of the control parameters is established, whose output are screw conveyor speed and advance speed at the next moment. The error reduction rate method is introduced to trim and identify the network structure to optimize the control model. On this basis, an optimal control system for earth pressure balance (EPB) of shield machine is established based on the direct inverse control method. The simulation results show that the method can optimize the control parameters coordinately according to the changes of the construction environment, effectively reduce the earth pressure fluctuations during shield tunneling, and can better control the stability of the excavation surface.

scholarly journals Burst pressure prediction of fiber-reinforced flexible pipes with arbitrary generatrix

2021 ◽  
Vol 16 ◽  
pp. 155892502199081
Author(s):  
Guo-min Xu ◽  
Chang-geng Shuai
Keyword(s):  
Transfer Matrix ◽  
Linear Equations ◽  
Burst Pressure ◽  
Fiber Reinforced ◽  
Flexible Pipe ◽  
Theoretical Derivation ◽  
Design And Optimization ◽  
Flexible Pipes ◽  
Novel Method ◽  
Winding Angle

Fiber-reinforced flexible pipes are widely used to transport the fluid at locations requiring flexible connection in pipeline systems. It is important to predict the burst pressure to guarantee the reliability of the flexible pipes. Based on the composite shell theory and the transfer-matrix method, the burst pressure of flexible pipes with arbitrary generatrix under internal pressure is investigated. Firstly, a novel method is proposed to simplify the theoretical derivation of the transfer matrix by solving symbolic linear equations. The method is accurate and much faster than the manual derivation of the transfer matrix. The anisotropy dependency on the circumferential radius of the pipe is considered in the theoretical approach, along with the nonlinear stretch of the unidirectional fabric in the reinforced layer. Secondly, the burst pressure is predicted with the Tsai-Hill failure criterion and verified by burst tests of six different prototypes of the flexible pipe. It is found that the burst pressure is increased significantly with an optimal winding angle of the unidirectional fabric. The optimal result is determined by the geometric parameters of the pipe. The investigation method and results presented in this paper will guide the design and optimization of novel fiber-reinforced flexible pipes.

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