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Lateritic soil stabilization by addition of steel slags
(2021-09-01)
Chaiyaput, S.
;
Ayawanna, J.
The addition of electric arc furnace slag and ladle furnace slag on strength improvement of lateritic soil was studied in this work. Liquid limit, plasticity index, and the California bearing ratio of lateritic soil mixed with the slags were determined in comparison to those of ordinary lateritic soil. A scanning electron microscope was used to confirm the effect of those two slags on microstructures related to chemical components of raw materials and the strength of lateritic soil. The deterioration of California bearing ratio, liquid limit, and plastic index values were obtained when the electric arc furnace slag was mixed in lateritic soil. Meanwhile, the California bearing ratio of lateritic soil was highly improved with the addition of ladle furnace slag, owing to the hydration reaction between water and excess lime in ladle furnace slag with free silica in lateritic soil. The values of the plasticity index were also comparable to the ordinary lateritic soil. Microstructures confirmed a highly compacted surface of mixed lateritic soil with ladle furnace slag. The ladle furnace slag is therefore one of the promising alternative low-cost materials for the soil-stabilizing application.
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Evaluation method on ground movement using continuum ground model
(2021-01-01)
Sugimoto, M.
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Chen, J.
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Anh, P. T.
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Manabe, K.
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Lam, L. G.
To analyze the ground movement and the influence of shield tunneling above tunnel structures, the continuum ground model with segmental lining is in use. The analysis region in the transverse section should confirm that the side boundaries do not give significant effects on the analysis results. On the other hand, the lower analysis region is selected based on the empirical value to fit the analysis result for the measured data in practice. The effects of tunnel excavation in the numerical analysis are classified into two parts: one is the unloading effect because of the removal of the soil weight at the tunnel section, and the other is the effect of stiffness reduction inside the tunnel. The former heaves the ground around the tunnel, of which the magnitude increases as the distance from the tunnel invert to the bottom of the analysis region increases. This influence increases as the ground stiffness decreases. This is because the numerical analysis is based on the stress–strain relationship and the displacement comes from the distance multiplying with strain in the case of the elastic model. The latter one causes the upper part of the ground around the tunnel to move toward the tunnel, which decreases the ground reaction. The analysis results include both effects. This study shows both effects on ground displacements separately, taking the lateral region size W and the lower region size d as parameters, and discusses the method to evaluate the analysis results.
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Successful mitigations of riverbank slope stabilizations and road failures caused by excessive rainfalls due to climate change at national road 1B (NR 1B) in Laos PDR
(2020-01-01)
Bergado, Dennes T.
;
Chaiyaput, S.
The sites of the successful road embankment and pavement repairs were located in Laos PDR at National Road 1B (NR 1B). National Road (NR) 1B connects Laos to China. Illustrations of the road embankment and pavement failures and their successful mitigations are discussed. The mitigations of the first case (Case 1) consist of PEC-150 geotextile reinforcements with gabions and wrapped around soil bag facing combined with intercepting trench drains wrapped around with TS-50 geotextiles. In the second case (Case 2), the proposed pavement repairs consisted of intercepting trench drains wrapped around with TS-50 geotextiles combined with PEC-150 geotextile reinforcements of the gravel sub-base replacing the upper portions of the embankments underlying the pavements. The intercepted subsurface seepage lowered the water table and collected and safely directed the seepage flow to drainage pipes and channels.
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Simulation on small diameter shield for pre-support method by numerical analysis
(2020-01-01)
Sugimoto, Mitsutaka
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Huynh, T. N.
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Chaiyaput, S.
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Lam, L. G.
;
Miki, A.
When the road shield tunnels are constructed in urban area, the construction of branch tunnels from a main road tunnel by non-open cut method is required. Therefore, a pre-support method using several small diameter shield tunnels above and below the main shield tunnel was proposed for soft ground under groundwater level. But the small diameter shield tunnel with three dimensional sharp curve has never been constructed before, since it is difficult to control the shield along the planned alignment. Therefore, the shield operation parameters were estimated theoretically and the shield behaviors were simulated to examine the possibility of the shield tunnels using a small diameter shield with 3D sharp curve. As a result, it was confirmed that the calculated shield behavior has a good agreement with the planned one, by adjusting the shield operational parameters.
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Effect of polymer and Portland cement on strengthen crushed rock for pavement base
(2019-01-01)
Chaiyaput, S.
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Bergado, D. T.
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Ayawanna, J.
The effect of concurrent use of liquid polymer and Portland cement as a reinforced material in crushed rock pavement base was investigated in this work. The strength of polymer-treated crushed rock (treated crushed rock) and ordinary crushed rock (untreated crushed rock) were characterized and compared. In strength analysis, the California bearing ratios (CBR) of untreated and treated crushed rock were determined under unsoaked and soaked conditions to simulate post-flood pavement damage. The unconfined compressive strength (UCS) was evaluated under unsoaked conditions for 2h, 1-day, 3-day, 7-day, and 28-day curing periods. The results showed that the CBR of untreated and treated crushed rock under soaked and unsoaked conditions were positively correlated with dry density. The CBR under the unsoaked condition of untreated crushed rock was identical to that of treated crushed rock. Meanwhile, under the soaked condition, the CBR of treated crushed rock was twice as higher than the untreated crushed rock. The swelling indices were 0% for both untreated and treated samples. The UCS of treated crushed rock showed positively correlation with the curing time. The use of liquid polymer and Portland cement, therefore, improved the strength of crushed rock pavement base in which effectively mitigate the post-flood pavement damage.
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Reconfirmation of Skempton-Bjerrum 2D to 3D settlement conversion using FEM of full scale embankments
(2018-06-01)
Chaiyaput, S.
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Bergado, D. T.
The soil is a production of natural process, which is highly variable with very complex properties, and soil behavior can be difficult to calculate. Numerical Simulation can be applied to deal with the numerous aspects of complex geotechnical structures. The 3D FEM simulation model can present the conditions of the geotechnical project in details and assumptions, which are similar to actual situations, but the process of running the 3D FEM analysis takes longer computer time. Therefore, 2D FEM simulation model is proposed to reduce calculation time, but the prediction results are usually overestimated. Accordingly, this paper re-analyzed the 2D analysis to represent the performance of 3D analysis based on Skempton-Bjerrum method. The simulated 2D and 3D FEM settlement results had been carried out and compared with the measured data of two full scale embankments including the dissipation of the excess pore pressure. Consequently, it was confirmed that predicted result of 2D and 3D FEM numerical simulation agreed with the correction of Skempton-Bjerrum method that can be applied to predict the final settlements in 3D conditions.
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Prefabricated Vertical Drain (PVD) and Deep Cement Mixing (DCM)/Stiffened DCM (SDCM) techniques for soft ground improvement
(2018-04-12)
Bergado, D. T.
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Long, P. V.
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Chaiyaput, S.
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Balasubramaniam, A. S.
Soft ground improvement techniques have become most practical and popular methods to increase soil strength, soil stiffness and reduce soil compressibility including the soft Bangkok clay. This paper focuses on comparative performances of prefabricated vertical drain (PVD) using surcharge, vacuum and heat preloading as well as the cement-admixed clay of Deep Cement Mixing (DCM) and Stiffened DCM (SDCM) methods. The Vacuum-PVD can increase the horizontal coefficient of consolidation, C<inf>h</inf>, resulting in faster rate of settlement at the same magnitudes of settlement compared to Conventional PVD. Several field methods of applying vacuum preloading are also compared. Moreover, the Thermal PVD and Thermal Vacuum PVD can increase further the coefficient of horizontal consolidation, C<inf>h</inf>, with the associated reduction of k<inf>h</inf>/k<inf>s</inf> values by reducing the drainage retardation effects in the smear zone around the PVD which resulted in faster rates of consolidation and higher magnitudes of settlements. Furthermore, the equivalent smear effect due to non-uniform consolidation is also discussed in addition to the smear due to the mechanical installation of PVDs. In addition, a new kind of reinforced deep mixing method, namely Stiffened Deep Cement Mixing (SDCM) pile is introduced to improve the flexural resistance, improve the field quality control, and prevent unexpected failures of the Deep Cement Mixing (DCM) pile. The SDCM pile consists of DCM pile reinforced with the insertion of precast reinforced concrete (RC) core. The full scale test embankment on soft clay improved by SDCM and DCM piles was also analysed. Numerical simulations using the 3D PLAXIS Foundation finite element software have been done to understand the behavior of SDCM and DCM piles. The simulation results indicated that the surface settlements decreased with increasing lengths of the RC cores, and, at lesser extent, increasing sectional areas of the RC cores in the SDCM piles. In addition, the lateral movements decreased by increasing the lengths (longer than 4 m) and, the sectional areas of the RC cores in the SDCM piles. The results of the numerical simulations closely agreed with the observed data and successfully verified the parameters affecting the performances and behavior of both SDCM and DCM piles.
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Mitigations of flooding and soil erosions geo-disasters in Thailand and Laos due to climate change: From Mountains to Lowlands
(2017-06-01)
Bergado, D. T.
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Chaiyaput, S.
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Voottipruex, P.
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Hino, T.
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Chanmee, N.
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 Pain Industrial Estate. Navanakom 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.

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