Effect of anisotropy and destructuration on behavior of Haarajoki test embankment

This paper investigates the influence of anisotropy and destructuration on the behavior of Haarajoki test embankment, which was built by the Finnish National Road Administration as a noise barrier in 1997 on a soft clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. The construction and consolidation of the embankment is analyzed with the finite-element method using three different constitutive models to represent the soft clay. Two recently proposed constitutive models, namely S-CLAY1 which accounts for initial and plastic strain induced anisotropy, and its extension, called S-CLAY1S which accounts, additionally, for interparticle bonding and degradation of bonds, were used in the analysis. For comparison, the problem is also analyzed with the isotropic modified cam clay model. The results of the numerical analyses are compared with the field measurements. The simulations reveal the influence that anisotropy and destructuration have on the behavior of an embankment on soft clay

A study on interaction between pile and prefabricated vertical drain in soft clay

Pile foundation and prefabricated vertical drain (PVD) are two well established techniques used by geotechnical practitioners when dealing with soft compressive foundation materials. Driven stakes or piles were adopted since man first attempted to build secure dwellings near streams and rivers, as mentioned by Fleming et. al., (2008). Indraratna et. al., (2015) pointed out that PVDs has been adopted by the industrial practice to form radial drainage in low permeability soil for a fast consolidation. Even though both pile foundation and pre-consolidation with PVDs are widely adopted as geotechnical solutions in many projects, limited attempts of combined use of PVDs and piles were reported in the literature (Bradshaw and Baxter, 2006; Holtz and Boman, 1974; and Tefera et. al., 2011). The potential benefits of combining two ground improvement methods were not studied sufficiently by researchers and engineers

PVD カイリョウ ジバン ニオケル モリド カジュウ ニヨル ソクホウ ヘンケイ ヨソクホウ

博士（工学）佐賀大

Theoretical and numerical perspectives and field observations for the design and performance evaluation of embankments constructed on soft marine clay

In this chapter, a two-demensional plane strain solution is adopted for the embankment analysis, which includes the effects of smear zone caused by mandrel driven vertical drains. The equivalent (transformed) permeability coefficients are incorporated in finite element codes, employing modified Cam-clay theory. Selected numerical studies have been carried out to study the effect of embankment slope, construction rate, and drain spacing on the failure of the soft clay foundation. Finally, the observed and predicted performances of well-instrumented full-scale trial embankments built on soft Malaysian marine clay have been discussed in detail. The predicted results agree with the field measurements

An analytical model of PVD-assisted soft ground consolidation

Prefabricated vertical drains (PVDs) are widely used to accelerate the dissipation of excess pore pressure in soft estuarine deposits in coastal areas under fill surcharge or vacuum preloading. Vacuum preloading can also control any lateral outward movement of the embankment toe, although excessive inward movement must be avoided. An equivalent 2D numerical modelling is proposed as a predictive tool for multi-drain conditions, but unlike a 3D simulation it has a greatly reduced computation burden. A unit cell model incorporating key factors such as the smear effect, vacuum distribution, nonlinear compressibility and permeability, soil disturbance and large-strain geometry, has also been developed. This paper presents selected work at the University of Wollongong on analytical solution for PVD-assisted ground improvement. The model is applied to a case history at Tianjin Port in China and then compared with the numerical result and field measurements

Creep analysis of an earth embankment on soft soil deposit with and without PVD improvement

In this paper, an anisotropic creep constitutive model, namely Creep-SCLAY1S is employed 10 to study the installation effects of prefabricated vertical drains (PVDs) on the behavior of a full 11 scale test embankment, namely Haarajoki embankment in Finland. The embankment was 12 constructed on a natural soft soil with PVD installed to improve the drainage under one half of 13 it. The Creep constitutive model used in this study, incorporates the effects of fabric 14 anisotropy, structure and time within a critical state based framework. For comparison, the 15 isotropic modified Cam clay (MCC) model and the rate-independent anisotropic S-CLAY1S 16 model are also used for the analyses. The numerical predictions are compared with field 17 measurements and the results indicate that the creep model provides an improved 18 approximation of field settlements, and excess pore pressure build-up and dissipations. In 19 addition, the application of two commonly used permeability matching techniques for two 20 dimensional (2D) plane-strain analysis of the PVD problem is studied and the results are 21 discussed highlighting their limitations and advantages

Back analyses on prefabricated vertical drain treated ground using plaxis 2D

By increasing the industrial developments in Malaysia, there are many construction projects has been carried out. With the development of construction project, it can cause reducing the construction area. Many of the construction nowadays need to be constructed on the soft ground due to the limitation area and it gives the problem of soil settlement and the construction cost directly become double. Prefabricated vertical drains PVD is one of the most commonly used techniques to reduce the time of settlement substantially. The purpose of this study is to study the performance of prefabricated vertical drain (PVD) as treated ground method. This paper presents a case study of the field data associated to settlement of treated soft soil using PVD by comparing with numerical simulation for embankment constructed along highway. This study involved two methods which are field settlement recorded and prediction of settlement using Finite Element Method. PLAXIS 2D analysis showed that the preloading is important to reduce the post construction settlement. Result from the case study indicates the settlement predicted from Finite Element Modelling is slightly higher compare to an actual field settlement. Drain spacing was analysed to evaluate the factor affecting the performance of prefabricated vertical drain. The rate of settlement was increase by decreasing of drain spacing. The installation of PVD at spacing 1.0m gives the optimum rate of settlement followed by spacing 1.4 m, 1.8 m and 2.0 m respectively. In terms of excess pore water pressure, the result showed the pore water pressure were significantly higher and dissipated slowly due to increasing of prefabricated vertical drain spacing. Based on the series of simulation conducted, it was found that the prefabricated vertical drain is effective pre-construction countermeasure for increasing ground stability

Prefabricated vertical drain in marine clay soil using plaxis 2D

Due to the rapid development in Malaysia, area that can be considered as suitable soil which has high resistance to support the structure naturally has becoming increasingly rare. This phenomenon has force engineers to works in soft ground with high compressibility layer. The main risk for development on soft soil is settlement. There are many researches that have been conducted in order to overcome this problem. Prefabricated Vertical Drain (PVD) is one of the methods used to accelerate the settlement, hence made it more suitable for development. This study aims to presents a case study of field data associated to settlement of treated marine clay soil using PVD with different spacing with finite element analysis. Data obtained from site instrumentation will be analysed by Asoaka method and shall be compared with PLAXIS 2D simulation analysis. The result shows that PVD was able to accelerate the consolidation process and suitable to be used as soft ground improvement technique. The rate of settlement was inversely proportional with the drain spacing. Based on the series of modelling it was proved that the prefabricated vertical drain is an effective method for increasing ground stability by accelerate the consolidation process thus suitable to be used as soft ground improvement technique and different PVD spacing affect the soil settlements analysis in term of settlement rate and excess pore water pressure

The Necessity of The Consideration of Permeability Modifier in Simulations of Clay Treatment Systems Incorporating PVDs and Surcharge

Three trial embankments as TS1, TS2, and TS3 that were built for the investigation of a soil treatment project in Bangkok were modeled and verified based on the reported data. To clarify the importance of integration of the hydraulic modifier function vs stress, in the verified models, the modifier functions were omitted and the FEM models were run in the absence of the function. It was shown that after the omission of the hydraulic modifier, the results were overestimated especially for the TS1 and TS2, which had smaller PVDs (prefabricated vertical drains) distance. For the TS1 embankment, the settlement increased from 0.78 m to 0.87 m in 210 days. In 365 days, the settlement increased from 1.27 m to 1.44 m. For the TS2 embankment, the settlement increased from 0.93 m to 1.67 m in 230 days. In 410 days, the settlement increased from 1.36 m to 2.27 m. For the TS3 embankment, the settlement increased from 1.15 m to 1.79 m in 230 days. In 410 days, the settlement increased from 1.52 m to 2.24 m. The inclusion of the hydraulic function that calibrates the model for every step of loading is essential in the modelling such problems. For the design phase, this function should be calculated from lab tests, preferably undisturbed samples that were bored from the site, and the resultant function be used as an inseparable part of modeling and calculations.Journal of Civil Engineering and Materials Applicatio