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Mitigations of flooding and soil erosions Geo-Disasters in Thailand and Laos due to climate change: From Mountains to Lowlands D. T. Bergado; S. Chaiyaput; P. Voottipruex; T. Hino; N. Chanmee
Lowland Technology International Vol 19 No 1, June (2017)
Publisher : International Association of Lowland Technology

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In 2011, Thailand has suffered from devastating flooding due to climate change. During this time, 2 typhoons from the Pacific area went straight across Vietnam to Northern Laos and Northern Thailand instead of the usual path to Taiwan and Japan. Subsequently, huge flooding damaged many infrastructures and overtopped flood protection dikes of many industrial estates and educational institutions in the Central Plain of Thailand such as at Hi-Tech Industrial Estate, Bang Pa- In Industrial Estate, Navanakorn Industrial Estate and Asian Institute of Technology, to name a few. The same phenomenon also occurred in neighboring Laos PDR which caused unusually heavy rains and widespread river flooding. Consequently, riverbank erosions accompanied by slope failures occurred at Xedon River in Pakse, Southern Laos due to saturation caused by high water levels accompanied by high velocity flow of the flooded river. To evaluate the stability of these mitigation structures, finite element and limit equilibrium methods were utilized. PLAXIS 2D software was used to analyze the slope protection schemes at low and high water levels incorporating the various supporting and reinforcing materials. Moreover, the PLAXIS 2D software was also utilized to predict the vertical deformations of improved flood control dikes with increased embankment height at different cases of flood water levels. In addition, the SLIDE software was used to predict the factor of safety by using limit equilibrium method for the various riverbank erosion protection structures. Furthermore, RESSA software was utilized to evaluate the slope stability of the erosion protection structures with geosynthetic reinforcements of Xedon riverbank in Pakse combined with gabions and mattresses. Laos PDR is mountainous with high elevations.

SELECTION OF SOFT CLAY PARAMETERS FOR BANGKOK LOWLAND DEVELOPMENT A. S. Balasubramaniam; S. R. Kim; D. G. Lirr; S. S. S. Acharya; T. H. Seah; D. T. Bergado
Lowland Technology International Vol 1 No 1, June (1999)
Publisher : International Association of Lowland Technology

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The paper stresses the importance of a sound understanding of the soil behaviour in both the limit equilibrium and numerical analysis in soil- structure interaction problems: deep foundation for tall buildings; foundation for elevated expressways, subways, ground improvements works, tunnels for water supply, natural gas supply, sewerage and drainage. In the limit equilibrium analysis the use of Hvorslev strength parameters is suggested while for lightly overconsolidated clays the strength to be referred as a frictional component. In the numerical analysis a realistic stress- strain model for the behaviour of soft clays for stress states below the state boundary surface is recommended.

EVALUATION OF THE PVD PERFORMANCE AT THE SECOND BANGKOK CHONBURI IDGHWAY (SBCH) PROJECT D. T. Bergado; A. S. Balasubramaniam; I. A. Chishtr; T. Ruenkrairergsa; Y. Taesiri
Lowland Technology International Vol 1 No 2, Dec (1999)
Publisher : International Association of Lowland Technology

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The soft Bangkok clay foundation at the Second Bangkok Chonburi Highway Project (SBCH) was improved using prefabricated vertical drains (PVD). Monitoring instruments such as surface settlement plates, deep settlement plates, inclinometers and piezometers were installed in the subsoil in order to observe the deformation behavior of the embankments under loading. The Department of Highways, Thailand, arranged for the monitoring and documentation of the deformation behavior. These monitored records, supplemented with the laboratory test results, were analyzed in order to verify the in-situ horizontal coefficient of consolidation of the soil as well as the rate and amount of settlement. The maximum surface settlement was calculated using one-dimensional consolidation theory, Skernpton-Bjerrurn method, as well as Asaoka's method. In addition, a one-dimensional FEM computer software, capable of calculating the consolidation of multi-layered soil, named PVD-SD was also used successfully to predict the rate and amount of settlement. Finally, the monitored deformation behavior was compared with the predictions during the design stage of SBCH to evaluate the performance of PVD. The amount of settlement predicted by Asaoka's method was in excellent agreement with the observed values, whereas the one-dimensional consolidation method, Skempton-Bjerrurn method and the PVD-SD FEM method showed some overprediction. The PVD performance at SBCH Project confirmed and validated the ground improvement by preloading and drainage on soft Bangkok clay.

ANALYTICAL MODEL OF HEXAGONAL WIRE MESH REINFORCEMENT WITH WEATHERED BANGKOK CLAY BACKFILL D. T. Bergado; P. Voottipruex; A. Asanprakit; C. Teerawattanasuk
Lowland Technology International Vol 3 No 2, Dec (2001)
Publisher : International Association of Lowland Technology

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An analytical method is proposed for determining the pullout resistance/pullout displacement relationship for both of PVC-coated and zinc-coated hexagonal wire mesh reinforcement. The parameters used in this analytical model were obtained from pullout testing programs, such as shear stiffness (ks) and initial slope of pullout bearing resistance (Eip). In addition, this method can predict the movement characteristics of both PVC-coated and zinc-coated hexagonal mesh during pullout. The displacements along the reinforcement axial stiffness and the friction resistance can be simulated by linear, elastic-perfectly plastic model. The hyperbolic model can be used to calculate the bearing resistance. Reasonable agreement between the predicted and measured pullout resistances were obtained. From the predicted values, the percentages of the friction resistances to the total pullout resistances are 18% and 16% for zinc-coated and PVC-coated wire mesh, respectively. Consequently, the bearing resistances are 82% and 84% of the total pullout resistances for zinc-coated and PVC-coated hexagonal wires,respectively. The ratios of friction resistances are 22% and 19% for the zinc-coated and the PVC-coated wire meshes, respectively. The total pullout resistances in the zinc-coated mesh is higher than PVC-coated mesh by approximately 20%. Furthermore, the weathered clay backfill was found to have higher pullout resitance and lower pullout displacement than the silty sand backfill.

INFLUENCE FACTORS ON THE LABORATORY TESTING OF GEOTEXTILES UNDER CONTROLLED ENVIRONMENT D. T. Bergado; S. Youwai; J. Maneecharoen
Lowland Technology International Vol 4 No 1, June (2002)
Publisher : International Association of Lowland Technology

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In order to investigate the influence factors affecting index and engineering properties of geotextiles under controlled environtments, different tests were conducted using both heat-bonded nonwoven and needle-punched nonwoven geotextiles, namely: apparent opening size (AOS), wide-width tensile strength, premittivity, transmissivity, and puncture resistance. The effect of humidity on the pore size og the samples was also investigated. To sheck whether the clamping system has an effect on the strength of geotextiles, over 24o tests were conduted. The presence of air bubbles in water and its effect on the permittivity and transmissivity of geotextiles were also verified. Also investigated were the effects of higher strain rate and displacement rate on the tensile strength and puncture resistancem respectively. The results indicate that decreasing humidity slightly increased the AOS; higher strain rate and the use of hydraulic clamp increased the wide-width tensile strength; using de-aired water largely improved the permittivity and transmissivity; and increasing the strain rate decreased the puncture resistance. The effects of humidity and oxygen content were more pronounced and obvious in the case of needle-punched geotextile compared to heat-bounded nonwoven geotextile.

THERMAL CONSOLIDATION OF SOFT BANGKOK CLAY H. M. Abuel-Naga; D. T. Bergado; S. Soralump; P. Rujivipat
Lowland Technology International Vol 7 No 1, June (2005)
Publisher : International Association of Lowland Technology

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Understanding the thermo-mechanical behavior of saturated fine grained soils has become a very important topic whenever the geotechnical problems involve thermal effects. Previous research works in literature show that by subjecting the saturated fine-grained soils to temperature less than water boiling point volumetric and shear strength changes are induced. The thermally induced changes have been attributed to the physico-chemical change at the microscopic level. The aim of this research is to study the thermo-mechanical behavior of natural soft Bangkok clay, with temperature up to 90OC. Intensive laboratory tests using modified oedometer apparatus were conducted to investigate this behavior. The testing program was directed to study the effect of heat on the thermally induced volume change at different temperature and stress conditions, the thermal evolution of the preconsolidation pressure, the induced overconsolidation behavior after heating/cooling cycle, and the effect of temperature on the hydraulic conductivity. The experiments carried out on soft Bangkok clay provided some additional useful data on the thermo-mechanical behavior of the soft deposits. The results of this research work have been compared with those in literature with different clay types to generalize the thermo-mechanical behavior of the saturated clays.

NOVEL THERMO-PVD CONSOLIDATION TECHNIQUE FOR SOFT SOILS C. Pothiraksanon; D. T. Bergado; H. M. Abuel-Naga; S. Hayashi; Y. J. Du
Lowland Technology International Vol 9 No 2, Dec (2007)
Publisher : International Association of Lowland Technology

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Previous research efforts on investigating the thermo-hydro-mechanical behaviour of fine grained soils as well as recent extensive experiments conducted on soft Bangkok clay have demonstrated that saturated fine-grained soils subjected to temperature less than boiling point of water (100OC) undergo volumetric and shear strength changes depending on the stress history. These features encouraged employing the thermal load only, up to 90OC, or in combination with mechanical loading as ground improvement technique. This paper addressed the applicability of this technique through a series of large oedometer tests conducted on soft Bangkok clay. Heating was achieved using flexible wire heater attached to the PVD point or using separate line heat source. The clay has been subjected to either thermal load or thermo-mechanical load. The test results show that a combination of the thermal and mechanical load gives promising results and is a viable technique since it accelerates the rate of consolidation and increases the amount of total settlement. This behavior can be attributed to the increase in the soil hydraulic conductivity as the soil temperature increases. Therefore, raising the soil temperature during the preloading period can enhance the performance of the PVD, particularly, by reducing the drainage retardation effects due to the smear zone around PVD.

CETEAU PVD VACUUM SYSTEM IN SOFT BANGKOK CLAY: A CASE STUDY OF THE SUVARNABHUMI AIRPORT PROJECT J. Saowapakpiboon; D. T. Bergado; S. Hayashi; J. C. Chai; N. Kovittayanon; T. P. de Zwart
Lowland Technology International Vol 10 No 1, June (2008)
Publisher : International Association of Lowland Technology

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A new improvement technique is currently applied for soft Bangkok clay combining capped PVD with vacuum pressure and embankment loading whereby the prefabricated vertical drains (PVD) are connected by PE tubes to a vacuum pump called “CeTeau PVD Vacuum System”. The method uses a surface soil layer as a sealing layer for leakage protection and there is no need to place air-tightening geomembrane sheets on the ground surface. This method has two advantages for situations of a) high air/water permeability layer exist near the ground surface, and b) combining vacuum pressure with embankment load. An actual field project combining PVD vacuum and embankment loading has just been completed. The performance data of the system during the improvement of the section EW-4, a part of the third runway of Suvarnabhumi International Airport, Thailand are presented and interpreted. The monitored data indicated that the system mobilized -60 kPa atmospheric pressure. This allowed for unprecedented loading and settlement rates during the construction of an embankment and achieved the required degree of consolidation within the specified time period. The prediction by PVDCON FEM Software generally agreed with the observed values. As expected, increasing the Kh/Ks and OCR values resulted in lower settlement values.

PERFORMANCE OF FULL SCALE TEST EMBANKMENT WITH REINFORCED LIGHTWEIGHT GEOMATERIALS ON SOFT GROUND T. Tanchaisawat; P. Voottipruex; D. T. Bergado; S. Hayashi
Lowland Technology International Vol 10 No 1, June (2008)
Publisher : International Association of Lowland Technology

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Embankment construction using reinforced lightweight geomaterials over soft ground will alleviate problems of instability and large settlements. Backfills of retaining structures can also be constructed using lightweight materials resulting in lower vertical loads and, consequently, reduced settlements. The aim of this study is to investigate the behavior of lightweight geomaterials consisting of tire chip-sand mixture reinforced with geogrids for use as embankment construction on soft ground. The experimental results indicated that the mixing ratio of 30:70 % was the most suitable fill material. The full scale field test embankment was constructed at the campus of Asian Institute of Technology (AIT) in Bangkok, Thailand. The geogrid reinforced embankment system was extensively instrumented in the subsoil and within the embankment itself in order to observe its behavior during construction and post construction phases, and thereby evaluate its performance. The unit weight of rubber tire chip-sand mixtures is about 75% lighter than conventional sand. The total settlement at ground surface is 67.5% less when compared to the conventional backfill without foundation treatments. The maximum lateral wall movement observed at 13 months after construction at top of wall is 45% smaller when compared to conventional sand backfill on untreated ground. Finally, the geogrid reinforcements correspond well with the bilinear type of maximum tension line.

SOIL REINFORCEMENT WITH COMBINATION ROOTS SYSTEM: A CASE STUDY OF VETIVER GRASS AND ACACIA MANGIUM WILLD P. Voottipruex; D. T. Bergado; W. Mairaeng; S. Chucheepsakul; C. Modmoltin
Lowland Technology International Vol 10 No 2, Dec (2008)
Publisher : International Association of Lowland Technology

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This paper focussed on the effect of combination root reinforcement system on soil slope stability. Consequently, an attempt was made to study the effect of Vetiver grass roots in combination with Acacia Mangium Willd roots on shear strength of soil. To assess the mechanisms of root anchorage and root reinforcement within two years growth period, the plants were pulled out to determine their pullout resistance as well as their penetration into the soil. In addition, large scale field direct shear tests were carried out on both rootless and root reinforced soil. A composite soil-root system was developed to evaluate the contribution of combination root reinforcement to shear strength. Subsequently, the results revealed that there are significant root reinforcement effects of 1.5 times increase by Vetiver grass and 3.0 times increase by Acacia tree in the soil shear strength root reinforcement in the slope stabilization scheme. Consequently, this paper proposed the critical zone and selected soil moisture content to calculate the strength increment of the combination root reinforcement soil system for successful slope stabilization.

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