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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.

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.

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.

BEHAVIOR OF STIFFENED DEEP CEMENT MIXING PILE IN LABORATORY P. Jamsawang; D. T. Bergado; A. Bhandari; P. Voottipruex
Lowland Technology International Vol 11 No 1, June (2009)
Publisher : International Association of Lowland Technology

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The low strength and stiffness of Deep Cement Mixing (DCM) pile causes unexpected failure that has been mitigated with the introduction of stiffened deep cement mixing (SDCM) pile. The SDCM is a new type of DCM pile reinforced by concrete core pile. In this paper, the interface behavior of SDCM pile and its strength have been studied by various laboratory tests. The cement content was varied from 10 to 20% by dry weight of clay and mixed at the water content corresponding to its liquid limit to obtain optimum strengths. The interface friction between the core concrete pile and the cement-admixed clay was studied by means of the direct shear tests and Ko interface shear tests. The 15% cement content yielded optimum interface shear strength. The CIU triaxial compression test of model SDCM pile revealed that the concrete core pile length should be more than 75% of the DCM pile length in order to have significant improvement.

Behaviors of soil cement columns and stiffened soil cement column wall in shallow excavation I. Meepon; P. Voottipruex; P. Jamsawang
Lowland Technology International Vol 18 No 3, Dec (2016)
Publisher : International Association of Lowland Technology

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This research aims to presents results of laboratory investigations on cement-admixed clay and full scale of soil cement column (SCC) walls and stiffened soil cement column (SSCC) walls of 60 cm in diameter and 8 m depth constructed in soft Bangkok clay in various forms. There are five types of wall namely, type A: three row of soil cement column, type B: two rows of soil cement column, type C: one row of cement column inserted with steel H-beam in each column, type D: one row of soil cement column alternately inserted with H-beam, and type E: one row of soil cement column without reinforcement. The shallow excavation was conducted step by step with depth increment 1 m to 5 meter. Immediately after excavation; it can be observed from inclinometer that the horizontal movement of all type of wall exhibited slightly different. However, one day after excavation; the type A wall exhibited minimum movement of 6.37 mm; follow by type B wall with movement of 15.76 mm, and type C wall with movement of 22.37 mm. The maximum movement was observed from type D wall with movement of 51.99 mm while the type E wall failed one day after excavation. Alternate H-shaped steel reinforcement in the soil cement wall resisted bending moment due to lateral earth pressure up to a certain excavation depth. Beyond this depth the bending moment decreased, and the horizontal movement of the wall exhibited rigid body translation mode. The SSCC wall resisted bending moment due to lateral earth pressure through the embedded H-shaped steel in the soil cement column. Strain values indicated that the horizontal force was transferred to the embedded steel. Horizontal movement at the pile cap increased as the horizontal force increased. The SSCC continuously resisted the horizontal force through the embedded H-shaped steel, and a linear relationship between horizontal load and horizontal displacement was observed.

Effectiveness of slurry wall for lead retention in contaminated soil C. Teerawattanasuk; P. Voottipruex
Lowland Technology International Vol 18 No 4, March (2017)
Publisher : International Association of Lowland Technology

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This paper examines the hydraulic conductivity and strength properties of several bentonite�cement (BC) mixtures and to delineate the influence of the cementitious material content, bentonite, and curing time upon the strength and hydraulic conductivity of BC barrier materials. The two ratios of cementitious material to bentonite-water slurry used were 7.5%, and 15%. Samples were cured for a period of 7, 14 and 28 days at 100% humidity, after which samples of each mixture underwent permeability and unconfined compression testing. It can be seen that unconfined compressive strength (qu) of specimen increased as cement content increased due to the hydration products. However, the qu of specimen decreased as bentonite content increased due to high expansion. Specimens with high cement content form a low permeability material that keeps high lead contaminant in top and middle portion in the specimen. The results shows that qu increase as cement content and curing period increase while the permeability coefficient decrease as curing period and cement content increase. Moreover, the effectiveness of slurry wall for lead retention contaminated soil can be obtained by using the optimum bentonite-cement proportion of B10C15.

Settlement-time curve calculation of soil-cement column and slab improved soft clay deposit S. Pongsivasathit; P. Voottipruex; J.C. Chai
Lowland Technology International Vol 19 No 2, Sep (2017)
Publisher : International Association of Lowland Technology

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The consolidation behavior of soft clayey deposit improved by a floating soil-column with a cement stabilized slab on the ground surface has been investigated by laboratory model test using a symmetric unite cell model and finite element analysis (FEA). The effects of thickness and undrained shear strength of slab on the relative penetration of column into surrounding soil were quantified. Based on the results, the method proposed Pongsivasathit et al. for calculating the settlement of a floating column improved soft subsoil has been modified. The main modification is the equation for calculating the value of Hc, which is the thickness of a soil layer at the bottom of the column improved zone. And in settlement calculation, Hc layer has been treated as an unimproved layer. The effectiveness of proposed method has been verified by comparing with the measurement results of field case histories and laboratory model tests.

Determination of Optimum Strength of Red Soil and Mixed Soil using Soil-Cement (S/C) Mix Ratio S Karki; S. Manandhar Manandhar; P. Voottipruex
Lowland Technology International Vol 22 No 1 (2020): Lowland Technology International Journal - Special Issue on: Engineering Geology
Publisher : International Association of Lowland Technology

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The research paper is focused on the improvement of the palaeolateritic red soil, clayey silt of low plasticity (ML) from Ratmatearea incorporating mixed with poorly graded sand with gravels(SP) from Helipad area inside the premises of Devghathydropower station, Nuwakot District, Nepal. With theconfirmation of maximum dry density (MDD) and optimummoisture content (OMC), 20% of SP was mixed homogenouslywith 80% of ML and experimented by adding cements at 3%,5%, 7% and 10% respectively. Hence ML and mixed soil(H20:R80) have been cured for 7, 14 and 28 days for thedetermination of undrained strength by UCS and pulse velocityby passing Pundit ultrasonic pulse velocity to check thecompactness of specimens. The Pearson’s coefficient ofcorrelation between UCS test and UPV revealed the strongpositive correlation linear relationship of 0.78. The linearregression model elucidates that for every additional undrainedstrength determined by UCS, the pulse velocity is expected to beenlarged by an average of 0.5135 m/s. Since, the cementadmixture of more than 7% impedes the rapid increase in pulsevelocity which was also confirmed by UCS tests due to thepresence of high capillary porosity of cement when excesscement was added. The study predicts that the optimum cementcontent for both soils in this research are best suitable at 7%admixture of cement when cured for 28 days.

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