scholarly journals Failure and Remediation of an Embankment on Rigid Column-Improved Soft Soil: Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Shaofu Gu ◽  
Weizheng Liu ◽  
Mengyuan Ge
Keyword(s):  
Bearing Capacity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Field Investigation ◽  
Design Stage ◽  
Overall Stability ◽  
Joint Quality

The south extension line was constructed as a new part of the Xintai Expressway in Guangdong Province, China. The project required the construction of an embankment over soft soil with a thickness of up to approximately 14.0 m, and prestressed pipe pile was selected for reinforcing the soft soil foundation to increase bearing capacity and reduce settlement. Embankment sliding with a length of approximately 110 m and cracking with a length that exceeded 300 m occurred before the construction of the pavement structure. Field investigation and theoretical analysis results indicate that the safety factor of the overall stability calculated by the existing code methods is overly large, thereby resulting in large design pile spacing, low design bearing capacity provided by single pile, and excessive load shared by subsoil between piles. These results all cause the flow sliding of soft soil between the piles and the bending fracture of some piles. The revised density method can be used to check the stability of flow sliding, and the bending moment of piles should also be checked during the embankment design stage. In addition, perpendicularity deviation and poor joint quality of pile construction also contributed to the reduction of the bearing capacity of the pipe piles and the overall stability of embankment. Reconstruction of additional rigid piles and add pile after drilling holes are adopted in the sliding and cracking sections to reinforce the failed embankment, respectively. The remediation effect was validated by the measured excess pore water pressure, subgrade settlement, and horizontal displacement.

Study on Artificial Island Ground Improvement Method and Effect

2014 ◽  
Vol 1030-1032 ◽  
pp. 1037-1040
Author(s):  
Jin Fang Hou ◽  
Ju Chen ◽  
Jian Yu
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Treatment Method ◽  
Surcharge Preloading ◽  
Porosity Ratio ◽  
Improvement Method ◽  
Consolidation Degree

The artificial island ground on an open sea is covered by thick soft soil. It must be improved before using. In accordance with a designing scheme, the ground treatment method is inserting drain boards on land and jointed dewatering surcharge preloading, the residual settlement is not more than 30cm after improvement and the average consolidation degree is more than 85%. In order to estimate ground improvement effect and construction safety, instruments are buried to monitor the whole ground improving processes. By monitoring settlement and pore water pressure, it is shown that the total ground settlement in construction is 2234mm, its final settlement is 2464mm, and consolidation degree and residual settlement respectively satisfy requirements. In ground improvement, horizontal displacement is small and construction is safe. Meanwhile, the results of soil properties and vane shear strength detection tests show the soft soil ground is greatly reduced in water content and porosity ratio, and improved in strength. It is named that the ground improvement method is reasonable and reaches expected effect.

scholarly journals PENURUNAN OPRIT JEMBATAN SEMARANG LINGKAR UTARA DAN JEMBATAN KALI JAJAR DEMAK JAWA TENGAH DENGAN PRE-FABRICATED VERTICAL DRAIN

2021 ◽  
Vol 4 (1) ◽  
pp. 27
Author(s):  
M Zaki ◽  
Wardani SPR ◽  
Muhrozi Muhrozi
Keyword(s):  
Bearing Capacity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soil Improvement ◽  
Unit Weight ◽  
Fast Time ◽  
Foundation Soil ◽  
Vertical Drain ◽  
Long Time

<p><em>Construction on soft soil, often creates problems. The Semarang North Ring Bridge and Kali Jajar Bridge are the Recent soft Marine Alluvium zones located in the Pantura area which have very soft soil characteristics with a depth of more than -30.0 meters this has resulted in a very large settlement due to very small grains, flood, rob, pore water pressure increases so that the shear strength of the soil will be small, the compression is large and the permeability coefficient is small so that if the construction load exceeds the critical bearing capacity, the damage to the foundation soil will occur. To get the increase in soil bearing capacity, it can be achieved by changing the properties of the soil from the shear angle (</em>f<em>), cohesion (c) and unit weight (</em>g<em>). The settlement can be reduced by increasing the cavity density from the compression of the soil particles (Wesley, 1977). Soil improvement takes a long time, aiming to increase shear resistance so that it requires a fast time in this case is to use Pre-Fabricated Vertical Drain (Bowles 1981). The results of the analysis of the pattern of decline and the effectiveness of the use of PVD (pre-fabricated vertical drain) at the Oprit Bridge in the two research locations have the same decrease in the range of the same heap height at (H = 4 meters) there is a decrease of 117.53 cm at 64 months on the bridge. Kali Jajar (STA. 3 + 200) and there was a decrease of 268.94 cm at 37 months at the Semarang North Ring Bridge</em></p>

scholarly journals A Study on the Seismic Response Characteristics of an Oblique Pile Group-Soil-Structure with Different Pile Caps

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Desen Kong ◽  
Yifei Bai ◽  
Yongpo Chen ◽  
Meixu Deng
Keyword(s):  
Soil Structure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Layer ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Pile Group ◽  
Vertical Displacement ◽  
Pile Groups ◽  
Cap Model

For the study of interaction between piles-soil-structure with different caps, the FLAC3D finite difference software was used as the research tool, and dynamic load was El Centro seismic wave. The numerical model of obliquely pile groups of the pile-soil-structure with low cap and high cap was established, respectively. The variation of pore pressure, the moment, the displacement of piles, and the displacement of pier was analyzed. The results indicate that under the action of earthquake, the distribution of pore water pressure in the soil layer increases gradually from top to bottom. The instantaneous negative value of partial soil due to shear dilation occurs at the peak of vibration acceleration. The middle area of the pile foundation in sandy soil is prone to liquefaction. In the same model, the maximum bending moment of inclined piles is greater than that of vertical piles. The vertical displacement of the vertical piles is a constant value along the depth, while the vertical displacement of the inclined piles is changed along the depth of the buried piles. In the high cap model, the horizontal displacement of the inclined piles is no longer monotonous along the burying depth, and the maximum value occurs in the sand soil layer. The vertical and horizontal displacements of the inclined piles and vertical piles in the high cap model are obviously greater than those of the low cap model. The maximum horizontal displacement of the pier of the two models occurs at the same time.

Geosynthetic Encased Column: comparison between numerical and experimental results

2021 ◽  
Vol 44 (4) ◽  
pp. 1-12
Author(s):  
Nima Alkhorshid ◽  
Gregório Araújo ◽  
Ennio Palmeira
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Experimental Tests ◽  
High Permeability ◽  
Soft Soils ◽  
Column Comparison ◽  
Surrounding Soil ◽  
Granular Column

The use of granular column is one of the ground improvement methods used for soft soils. This method improves the foundation soils mechanical properties by displacing the soft soil with the compacted granular columns. The columns have high permeability that can accelerate the excess pore water pressure produced in soft soils and increase the undrained shear strength. When it comes to very soft soils, the use of granular columns is not of interest since these soils present no significant confinement to the columns. Here comes the encased columns that receive the confinement from the encasement materials. In this study, the influence of the column installation method on the surrounding soil and the encasement effect on the granular column performance were investigated using numerical analyses and experimental tests. The results show that numerical simulations can reasonably predict the behavior of both the encased column and the surrounding soil.

scholarly journals Perbandingan Pengujian Konsolidasi Menggunakan Alat Rowe Cell dan Oedometer pada Tanah Lanau Lunak

2020 ◽  
Vol 22 (2) ◽  
pp. 149-155
Author(s):  
Iskandar ◽  
Rabiya
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soil Samples ◽  
Soil Parameters ◽  
Soil Consolidation ◽  
Test Results ◽  
Soft Soils ◽  
Better Than ◽  
Rowe Cell

Soil consolidation testing using an oedometer and rowe cell. Oedometers are often used on clay and soft soils. However, in the development of the rowe cell device, the results of lowering soft soil were better than the oedometer. The advantage of this rowe cell is that it can determine the saturation value of the soil samples tested. The rowe cell tester can measure the pore water pressure at the beginning and end of each consolidation stage. This rowe cell can provide suitable settlement for soft soils. This consolidation test to obtain soil parameters such as Cv and Cc by using the rowe cell tool. After that, from the test results, the two tools were compared.

scholarly journals Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qizhi Hu ◽  
Qiang Zou ◽  
Zhigang Ding ◽  
Zhaodong Xu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Confining Pressure ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Excess Pore Water Pressure ◽  
Accurate Expression ◽  
Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

scholarly journals Experiment Study of Lateral Unloading Stress Path and Excess Pore Water Pressure on Creep Behavior of Soft Soil

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Wei Huang ◽  
Kejun Wen ◽  
Dongsheng Li ◽  
Xiaojia Deng ◽  
Lin Li ◽  
...  
Keyword(s):  
Pore Water ◽  
Creep Behavior ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Stress Path ◽  
Deviatoric Stress ◽  
Excess Pore Water Pressure ◽  
Pore Water Pressures ◽  
Excess Pore

The unloading creep behavior of soft soil under lateral unloading stress path and excess pore water pressure is the core problem of time-dependent analysis of surrounding rock deformation under excavation of soft soil. The soft soil in Shenzhen, China, was selected in this study. The triaxial unloading creep tests of soft soil under different initial excess pore water pressures (0, 20, 40, and 60 kPa) were conducted with the K0 consolidation and lateral unloading stress paths. The results show that the unloading creep of soft soil was divided into three stages: attenuation creep, constant velocity creep, and accelerated creep. The duration of creep failure is approximately 5 to 30 mins. The unloading creep behavior of soft soil is significantly affected by the deviatoric stress and time. The nonlinearity of unloading creep of soft soil is gradually enhanced with the increase of the deviatoric stress and time. The initial excess pore water pressure has an obvious weakening effect on the unloading creep of soft soil. Under the same deviatoric stress, the unloading creep of soft soil is more significant with the increase of initial excess pore water pressure. Under undrained conditions, the excess pore water pressure generally decreases during the lateral unloading process and drops sharply at the moment of unloading creep damage. The pore water pressure coefficients during the unloading process were 0.73–1.16, 0.26–1.08, and 0.35–0.96, respectively, corresponding to the initial excess pore water pressures of 20, 40, and 60 kPa.

scholarly journals Influence of Soil Structure on the Mechanical Response of Soft Soil

2018 ◽  
Vol 38 ◽  
pp. 03027
Author(s):  
Bin Bin Xu
Keyword(s):  
Yield Stress ◽  
Pore Water ◽  
Soil Structure ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Before And After ◽  
Strain Relationship ◽  
Consolidation Behavior

Usually the natural sedimentary soils possess structure more or less, which makes their mechanical response much different from the fully remolded soils. In this paper, the influence of soil structure on the mechanical response such as compressibility, shear, permeability is literately reviewed. It is found that the compressibility and consolidation behavior of structured and remolded soils can be divided clearly before or after the structural yield stress. The stress-strain relationship can be divided into two segments before and after the structural yield stress. Before the yield stress, the curve is elevating and after the yield stress the curve is decreasing. The increasing rate of pore water pressure increases after the soil reached yield stress.

scholarly journals Numerical Modelling of Prefabricated Vertical Drain for Soft Clay Using ABAQUS

2015 ◽  
Vol 773-774 ◽  
pp. 1502-1507
Author(s):  
Saiful Azhar Ahmad Tajudin ◽  
Mohd Fairus Yusof ◽  
I. Bakar ◽  
Aminaton Marto ◽  
Muhammad Nizam Zakaria ◽  
...  
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soft Clay ◽  
Elastic Model ◽  
Clay Layer ◽  
Soil Consolidation ◽  
Consolidation Process ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain

Construction, buildings and infrastructure founded on soft clays are often affected by settlement problem. Therefore, Prefabricated Vertical Drain (PVD) is one of the best solutions to accelerate soil consolidation by shortening the drainage path. In this study, numerical investigation was carried out to pursue a better understanding of the consolidation behavior of soft clay improved with PVD. The consolidation process accelerated by PVD with surcharge of 50 kPa was analysed using the ABAQUS software by adopting an elastic model. The aim of this study is to compare the settlement and the required time to fully consolidate the soft soil at different drain spacings (1.0 m, 1.5 m and 2.0 m) for two different thickness of the clay layer. The results shows that the time required to completely consolidate the soft soil for 12 m and 20 m thickness of clay layer with different spacings are in the range of 3 months to 66 months. The settlement rate and excess pore water pressure dissipation are increased when the spacing of the drain closer.

scholarly journals Vertical and Lateral Bearing Capacity of FRP Composite Sheet Piles in Soft Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zhe Wang ◽  
Shuwei Wu ◽  
Kaiwen Weng ◽  
Wangjing Yao ◽  
Sifa Xu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Yangtze River Delta ◽  
Composite Foundation ◽  
Sheet Pile ◽  
Composite Sheet ◽  
Frp Composite ◽  
Vertical Bearing ◽  
Full Scale Tests

Fiber-reinforced polymer (FRP) composite sheet piles are usually favored for slope and river-retaining structures due to their construction and environmental efficiency. Their applications, however, have been hindered by the lack of understanding of the bearing capacity. This paper studies the vertical and lateral bearing capacity of FRP composite sheet piles through three full-scale tests conducted in Haiyan, a soft soil site in the Yangtze River Delta of China. In the three tests, we measured the vertical bearing capacity of the FRP composite sheet piles, the bearing capacity of the composite foundation, and the lateral capacity of the FRP composite sheet piles, respectively. The test results show that the Q-S (load on the top of the pile versus settlement) curve of the FRP composite sheet piles exhibits a steep fall while that of the composite foundation is relatively flat. Moreover, the ultimate bearing capacity of the FRP composite sheet piles is measured to reach 23.8 kN while that of the composite foundation increases by 47.1 %, reaching 35.0 kN. It shows that the FRP composite sheet piles under the composite foundation have a favorable bearing performance. Finally, the final horizontal displacement of the FRP composite sheet pile in the reinforced area with anchoring the sheet pile is smaller than the final horizontal displacement in the nonreinforced area, indicating that the horizontal bearing capacity can be significantly improved by anchoring the sheet pile.

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