Soft Bangkok Clay Research Articles

Effect of Vehicle Cyclic Loading on the Failure of Canal Embankment on Soft Clay Deposit

Road embankments along irrigation canals, constructed on soft Bangkok clay, have always been unstable. Numerous studies have shown that rapid drawdown of water level may be one of the main causes, while vehicle cyclic loading may also contribute to embankment failure. This study aims to investigate the impact of vehicle loading on the failure of embankments built on Bangkok soft clay. The behavior of soft Bangkok clay under vehicle load has been investigated by employing conventional and dynamic triaxial techniques, and finite element method (FEM). This study also examined the effects of soft clay thickness and cyclic loading with different magnitudes and frequencies. The laboratory testing results indicate that the threshold stress of the soft clay is estimated to be approximately three-fourths of the undrained shear strength of the soil. The reduction in effective stress in the soft clay is caused by varied frequencies and thicknesses of the clay. Based on the analysis results, it has been proven that the cyclic loads exerted by vehicles solely are insufficient to cause the embankment to collapse. Nevertheless, the repetitive loading of vehicles may result in a one-quarter decrease in the embankment’s factor of safety.

Environmentally friendly binders from calcium carbide residue and silica fume and feasibility for soft clay stabilization

This investigation elucidates the development of an innovative, sustainable binder derived from calcium carbide residue and silica fume, aimed at enhancing soft clay stabilization with minimal environmental impact. Various mixtures were examined, focusing on the CaO to SiO2 molar ratio (Ca/Si), which varied from 1.85 to 0.65. Comprehensive analyses of the raw materials and pastes, including chemical composition, phase evolution, and microstructure, were conducted using techniques like Energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Results indicate a significant impact of raw material fractions on the compressive strength and cementitious properties. The mixture with a Ca/Si of 1.55 demonstrated the highest long-term strength, attributed to increased C–S–H content. A mixture of 30 wt% calcium carbide residue and silica fume was found to improve the unconfined compressive strength of soft Bangkok clay by 84% compared to 10 wt% ordinary Portland cement, demonstrating its efficacy and potential for widespread application in green construction initiatives. This research not only promotes the recycling of industrial by-products, reducing environmental impact, but also represents a significant advancement in sustainable construction materials.

Innovative solution: soil cement column walls as a temporary retaining structure for excavation in soft Bangkok clay

The installation of temporary retaining walls for excavation activities is considered a crucial and costly aspect in the realm of geotechnical engineering construction. Several past studies have been undertaken on the stability aspects of the deep mixing method for soil–cement column walls in soft Bangkok clay are available. However, there has been a lack of research focusing specifically on the relationship between execution time, cost, and stability of these walls, a topic on which this study is focused. The principal aim of this research was to investigate and make a comparative analysis of the stability, construction cost, and construction duration of retaining walls under varying construction site conditions. This study placed particular emphasis on shallow excavation conducted in the context of soft Bangkok clay, and its focus was to determine the most effective construction management strategies within the given contextual parameters. The investigated wall systems comprised of soil–cement columns (SC), stiffened soil–cement columns (SSC), and sheet pile walls. The SC had a diameter of a diameter of 0.6 m, while the SSC was composed of an embedded steel pipe with a diameter of 0.2 m (SSC-IRow Wall). The stability of the walls under investigation was assessed through the utilization of finite element (FE) simulation. The finite element model was initially calibrated through a comparison between the simulation results and the data obtained from field measurements. For a 4.5 m deep excavation with a required factor of safety > 1.3, the SCC and SSCC Walls were found to have an advantage over the conventional sheet pile wall. The SC Wall, consisting of two rows and measuring 7 m in length, demonstrated superior efficiency in terms of both time and cost, regardless of whether it was implemented in unconfined or confined construction sites. The utilization of the SSC-IRow Wall was suggested as an alternative in cases where the use of a thick SC Wall was prohibited. A systematic approach for the selection and design of the SC and SSC Wall systems was proposed, drawing upon a thorough examination and evaluation of the study findings. The results of this study possess the capacity to be utilized in excavation endeavors encompassing diverse depths in the context of soft Bangkok clay and comparable soil conditions.

Application of a cement–clay–air foam mixture as a lightweight embankment material for construction on soft clay

Lightweight air foam materials can be used in pavement structures, for example, as embankments and subbase and base layers. Soft clay can be mixed with cement and air foam to generate a lightweight material. However, most previous studies have presented only laboratory test results for these materials and have not shown real-world applicability. The current study aims to demonstrate the application of a cement–clay–air foam mixture as a lightweight embankment material to reduce the settlement of soft Bangkok clay foundations induced by embankment weight. An experimental investigation to determine unconfined compressive strength (qu) was initially conducted in the laboratory to establish the ideal quantities of soft clay, air foam, and ordinary Portland cement required for embankment construction using the clay mixture. A full-scale lightweight embankment of area 14 m × 14 m and height 2.5 m was constructed on an 11 m thick soft clay layer to observe embankment settlement behavior on the soft clay foundation. The qu values of the lightweight materials obtained from the site were 1.3–1.8 times higher than those in laboratory tests. The mixtures with wet field unit weights of 0.6, 0.8, and 1.0 kN/m3 exhibited qu values of 430–620 and 770–1000 kPa, respectively, higher than the standard requirements (> 100 kPa for 7 curing days and > 200 kPa for 28 curing days). Based on monitored data, the lightweight embankment reduced settlement by as much as 80 % compared with a traditional embankment. Therefore, lightweight clay materials are recommended for use in the construction of road embankments on soft clay.

Use of Cement and Bottom Ash in Deep Mixing Application for Stabilization of Soft Bangkok Clay

Use of Cement and Bottom Ash in Deep Mixing Application for Stabilization of Soft Bangkok Clay

Bridge approach settlement mitigation using expanded polystyrene foam as light backfill: Case study and 3D simulation

This paper presents the behavior of the bridge approach structure, which was repaired by using expended polystyrene foam as a replacement fill on Soft Bangkok Clay. The bridge approach began construction 20 years before a project. The settlement from consolidation and ground subsidence was high at 1.35 m at the end of the bearing unit before remedial measures. The settlement of the bridge approach structure before the project began and after completion was presented. After remedial measures, settlement rates tend to decrease after 100 days. The behavior of the bridge approach structure was modeled by using finite elements. The time-dependent strain of EPS geofoam can be predicted by an empirical equation by optimizing method. 3-dimensional finite element analysis can predict the overall behavior of bridge approach structure using EPS as fill material with time-dependent stiffness. The prediction before and after remedial measurement of the embankment was using similar model parameters. Important considerations to simulate EPS embankment behavior were long-term stiffness degradation of EPS block and ground subsidence.

Properties of soft Bangkok clay stabilized with cement and fly ash geopolymer for deep mixing application

Deep mixing (DM) is a technique for improving the ground that has been widely used worldwide. Ordinary Portland cement (C) has historically been the most popular binder for DM application; however, utilizing C releases a large carbon footprint. This research investigates the properties of soft Bangkok clay (SC) stabilized with C and high calcium fly ash (FA) geopolymer for high-strength soil–cement columns. The effect of influence parameters on the unconfined compressive strength (UCS) and scanning electron microscope (SEM) properties of SC-C-FA geopolymer specimens was measured. The specimens had initial water contents (w) of 1LL, 1.5LL, and 2LL, FA:C ratios ranged from 100:0–70:30, and sodium silicate:sodium hydroxide ratios (NS:NH) of 50:50, 70:30, and 80:20. The results indicated that the UCS of SC-C-FA geopolymer specimens was found to increase with the increasing C content. Whereas, the UCS decreased with the decreasing NS:NH ratios. The highest 28-day UCS of the specimen was obtained with initial water content of 1.5LL, FA:C ratio of 70:30, and NS:NH ratio of 50:50. The 28-day UCSs of SC-C-FA geopolymer with all initial water contents, C content greater than 5%, and NS:NH ratio of 50:50 passed the minimum UCS requirement for soil–cement columns. Furthermore, the equations for predicting UCS and carbon emissions of SC-C-FA geopolymer are very useful for designing soil–cement columns.

Electrical resistivity survey for evaluating the undrained shear strength of soft Bangkok clay at some of the canal-side road investigation sites

Electrical resistivity survey for evaluating the undrained shear strength of soft Bangkok clay at some of the canal-side road investigation sites

Improving mechanical properties and shrinkage cracking characteristics of soft clay in deep soil mixing

Deep soil mixing is a ground improvement method that enhances the characteristics of soft soils by mechanically mixing the soil with cementitious binders such as cement and fly ash (FA). The objective of this paper is to investigation the post-treatment mechanical properties and shrinkage cracking characteristics of soft Bangkok clays treated with ordinary Portland cement (OPC) and FA. Unconfined compressive strength, modulus of elasticity, and shrinkage cracking after 7 and 28 days of mixture curing were measured. The effects of wet/dry cycling on the durability of mixtures were examined. Microstructures of treated soft clays were examined using scanning electron microscopy with energy dispersive x-ray analysis (SEM/EDX) techniques. Test results showed that strength and stiffness improvements of stabilised soft clays increased with OPC content but decreased with FA content, while the extent of sample shrinkage decreased with increasing FA content. Based on these results, we propose the preliminary guideline of applying 15% replacement of OPC with FA to obtain the optimal mixture ratios that allows FA to act as a shrinkage-reducing agent for deep soil mixing purposes. By adding OPC and 15% FA at a binder-per-water ratio (B/wc) of 0.4, the stabilised soft clay satisfied both strength and shrinkage cracking criteria for deep soil mixing purposes. SEM/EDX analyses further supported these experiment results. In addition, correlations between the mechanical properties and the chemical compositions of stabilised soft clay were derived and presented.

Vacuum-PVD Improvement: a Case Study of the Second Improvement of Soft Bangkok Clay on the Subsiding Ground

Vacuum-PVD Improvement: a Case Study of the Second Improvement of Soft Bangkok Clay on the Subsiding Ground

Composite contiguous pile wall and deep mixing column wall as a dam –Design, construction and performance

This paper presents a case study on the application of a composite contiguous-pile wall and deep mixing (DM) column wall as a dam to develop a luxury lake in Lake Legend Chaengwatthana project, Bangkok, Thailand. This dam was constructed in a deep rainwater pond without providing the water removal, which could save on both time and cost construction. The design and construction method were challenging because the dam was located on the soft and thick Bangkok clay. The dam was designed by finite element analyses (FEA) using PLAXIS software. The 2 rows of contiguous-pile walls were first executed and then filled with soft clay. The DM columns were used to strengthen the clay backfill. The FEA results at normal and rain-shortage stages confirm the stability of the dam with accepted deformation. With insignificant water seepage over time, the dam acted as the waterproof barrier. The field performance of the dam during construction and at service state over 276 days were recorded and compared with FEA results. The numerical simulation slightly over-predicted the lateral displacement. The difference in the displacement between the measured and simulated data reduced significantly with depth. The rate of consolidation by the numerical simulation results were slightly slower than that by the field measurement. The outcome of this research will be fundamental to develop a design guideline of ground improvement in soft Bangkok clay and other similar soft clay deposits especially in Southeast Asian countries.

Large scaled field tests on soft Bangkok clay

In this lecture the interpretations of fully instrumented tests embankments and their role in the development of appropriate ground improvement techniques for highways, motorways and airfields on soft clay deposits is illustrated through well documented case studies in Bangkok, Thailand and Muar Flat Site in Kuala Lumpur. For the Bangkok Plain and with sand backfills the performance of embankments with different schemes of vertical drains was evaluated over a period of 25 years. Aspects such as recharging effects due to the drains, inadequate measures in maintaining vacuum during vacuum applications and possible hydraulic connections with large diameter drains are discussed. For the Muar test embankments, the role of fill strength in residual soil embankment and the field deformation analysis in separating consolidation settlement from immediate settlement and creep settlements is presented. Novel interpretations of settlement from pore pressure dissipations, secondary settlement from field measurements and decay of lateral deformation rate with time were also made.

Case study and numerical simulation of PVD improved soft Bangkok clay with surcharge and vacuum preloading using a modified air-water separation system

This manuscript presents the case study of soft Bangkok clay improvement and simulations using combined vacuum pressures with pre-existing surcharge embankment preloading, including installations of air-tight membranes and horizontal prefabricated drains connected to the top of the PVDs as well as to the vacuum system with a modified air-water separation system. The 17-m-long PVDs were installed from the top of the embankment in a triangular pattern at a spacing of 0.9 m. Monitoring instruments were installed to measure surface settlements, lateral movements, and pore water pressures in the soft clay layer. The subsequent analyses included settlement calculations, settlement predictions using observational methods, flow parameter back-calculations, soil property comparisons before and after improvement, and FEM simulations. The very soft to soft clay was transformed to medium-stiff clay because its undrained shear strengths and maximum past pressures increased, and its water contents, void ratios, and compression indices decreased. The analyses of the degree of consolidation utilized one-dimensional and observational methods as well as a numerical simulation for the prediction of consolidation settlements and comparison to the field data. The results illustrated the effectiveness of the modified vacuum-PVD system. The findings could be used for guidance of similar soft clay improvement projects.

Finite element analyses of rate-dependent thermo-hydro-mechanical behaviors of clayey soils based on thermodynamics

Clayey soils in the vicinity of energy geostructures may be exposed to long-term periodic thermal cycles. The creep and consolidation behaviors of the clayey soils can be both rate-dependent and temperature-dependent, and the underlying physical mechanisms are merely investigated theoretically. In this study, based on the theory of thermodynamics, a fully coupled thermo-hydro-mechanical (THM) finite element (FE) program for saturated soils is developed for this purpose. The FE formulation accounts for the combined effect of rate and temperature through the novel concept of granular temperature. Simulations of THM coupled validation cases and a series of experimental observations on the soft Bangkok clay are carried out. The obtained numerical results exhibit good agreement with analytical solutions and laboratory measurements. It is found that three fundamental physical mechanisms contribute to the irreversible thermal contraction observed for normally consolidated and lightly overconsolidated clays under drained thermal cycles: (1) the thermal creep excited by mass exchange from adsorbed water to free water; (2) the mechanical creep induced by confining stresses; and (3) the increase in granular packing caused by the thermal expansion of soil particles. The thermal contraction generally stabilizes within a few thermal cycles, as a result of the noticeable reduction in the thermal creep rate. It is further demonstrated that the transient heat transfer and the heating rate can greatly influence the deformation of clays subjected to thermal cycles.

Soil–Cement Screw Pile: Alternative Pile for Low- and Medium-Rise Buildings in Soft Bangkok Clay

AbstractBangkok clay is a soft marine clay with high water content and low bearing capacity. Bored piles installed by the dry process commonly are used for low- to medium-rise buildings in the metr...

Evaluation of polyvinyl alcohol and high calcium fly ash based geopolymer for the improvement of soft Bangkok clay

Soft Bangkok clay (SC) is recognized as a problematic soil in Thailand. This research investigates the possibility of using polyvinyl alcohol (PVA) and high calcium fly ash (FA) geopolymers to improve the strength of SC in deep soil mixing applications. The liquid alkaline activator (L) was composed of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). The studied influence factors included FA content, water content, L content, Na2SiO3/NaOH ratio, PVA concentration, PVA content, and curing time. Strength development and microstructure in the PVA-FA geopolymer stabilized SC were evaluated via the unconfined compressive strength (UCS) test and scanning electron microscope (SEM) test. The optimum ingredient considering workability and cost of FA geopolymer stabilized SC was found to be at a mix design of 1.0LL, Na2SiO3/NaOH = 1, FA = 40% and L/FA = 0.6, whereby a 28-day UCS of 1026 kPa was attained. The optimum PVA content and PVA concentrations were found at 15% and 4%. The 7-day and 28-day UCS values were improved by PVA up to 40% and 42% compared to those of the specimen without PVA, respectively. The outcome of this research will promote the usage of PVA-FA geopolymer as an alternative green soil stabilizer alternative to Portland cement for a DM improved soft Bangkok clay.

Bagasse ash–fly ash-geopolymer-treated soft Bangkok clay as subgrade material

A geopolymer was investigated as a low-carbon dioxide emission binder for soft Bangkok clay improvement. Bagasse ash (BA), an industrial by-product, was used as the main precursor, while fly ash (FA) was used as a supplementary to develop a geopolymer. A mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as a liquid alkaline activator. The unconfined compressive strength, q u, of the geopolymers was found to be directly dependent on the precursor (BA and FA) to liquid alkaline solution (P:L) ratio, sodium hydroxide concentration, FA:BA ratio and curing time. The geopolymer binder with P:L = 55:45, BA:FA = 70:30, sodium silicate:sodium hydroxide = 2:1 and sodium hydroxide concentration = 16 M was selected to treat Bangkok clay based on engineering and economic perspectives. The q u improvement with geopolymer content was divided into active and inert zones. The 10% geopolymer content was found to be the threshold limit. Beyond this limit, the q u improvement was insignificant. The 5% geopolymer content could improve the q u of soft Bangkok clay to meet the minimum requirement for subgrade according to the local road authority. The outcome from this research will promote the BA–FA geopolymer as a cleaner binder by using recycled waste materials in ground improvement applications.

SEA-LEVEL RELATED ENGINEERING GEOLOGY AND INTRINSIC COMPRESSION BEHAVIOUR OF BANGKOK CLAYS

All the important infrastructures in Bangkok city are founded in soft, stiff to hard clay layers up to 80 m deep. The engineering properties of these clays depend a lot on their microstructure, which in turns is a result of geological conditions governing the deposition and subsequent geological processes of loading, unloading and weathering. Thus, a study of soil microstructure would help understand better the soil engineering properties to be used in geotechnical analyses. In this paper, a detailed review of sea level-related engineering geology of the depositional environment of Bangkok clays was made. Geotechnical boreholes were drilled at six testing sites as part of a groundwater recovery study project, from which samples of Bangkok clays were collected up to 80 m deep and tested. Based on the results of an integrated geological-geotechnical analysis the microstructure of Bangkok clays was indirectly investigated via their intrinsic compression behavior and in-situ state. It was found that the Soft Bangkok clay at depth 4-11m (SOCL) is a bonding-dominated or cemented clay with a meta-stable structure, whereas stiff clay at depth 12-24m (STCL), the first hard clay at depth 30-50 m (HCL01) and the second hard clay at 50-80 m (HCL02) are fabric dominated with a stable structure. On the plots of void index versus depth the in-situ state the Bangkok soft clay lie in the sedimentation compression range, the stiff clay and the first hard clay lie both in sedimentation compression and overconsolidated clay ranges, while the second deeper hard clay (HCL02) lies only in the overconsolidated clay range.

Stabilization of Soft Bangkok Clay Using Portland Cement and Calcium Sulfoaluminate-Belite Cement

The present study investigates the mechanical properties of soft Bangkok clay which was stabilized by ordinary Portland cement and calcium sulfoaluminate-belite (CSAB) cement. The CSAB cement was synthesized by using several types of industrial waste materials such as marble dust waste and flue gas desulfurization gypsum. The raw materials were mixed in designed proportion and calcined at 1,250 °C for 2 hours. The X-ray diffraction patterns suggested the clinker consists of ~58% of ye'elimite and ~35% of belite. The slurry soft Bangkok clay with liquidity index of 1.0, 1.3 and 1.5 was stabilized with ordinary Portland cement and CSAB cement in the range of 5 - 20%. Based on the laboratory study, mechanism of rising unconfined compressive strength results which soft clay stabilized with CSAB cement could observe from Scanning Electron Microscope images.

Effectiveness of deep cement mixing walls with top-down construction for deep excavations in soft clay: case study and 3D simulation

This paper presents the observed and simulated effectiveness of deep cement mixing walls created using top-down (DCM-TD) construction techniques for a deep excavation in soft Bangkok clay. The wall system consisted of four rows of 0.7-m-diameter DCM columns, and the bracing system consisted of two 0.25-m-thick basement slabs and seven temporary struts. The effectiveness of the wall system compared to that of other wall systems was evaluated using the measured results of previous case studies. A 3D numerical analysis was performed to calculate forces in the basement slabs and bending moments in the DCM wall. Finally, series of parametric analyses of both DCM-TD and deep cement mixing walls created using bottom-up (DCM-BU) construction techniques were carried out, and their results were compared to highlight the effectiveness of DCM-TD and its applicability to excavations at greater depths. The field and numerical results show that DCM-TD is more effective than DCM-BU in terms of the limitations of lateral wall movement, the bending moment in a DCM wall and the thickness of a DCM wall for various depths because of a larger system stiffness. Therefore, DCM-TD is very effective and suitable for use in potential future deep excavations in urban areas.