Bangkok Subsoils Research Articles

Statistical Characterisation of the Geotechnical Properties of Bangkok Subsoil

Statistical Characterisation of the Geotechnical Properties of Bangkok Subsoil

Correlation between Engineering Properties of Bangkok Clay and Penetration Resistance of Screw Driving Sounding (SDS)

Adequate knowledge of soil properties is crucial before commencement of any engineering project, for which, in-situ tests are mainly popular in recent days. Many of those field tests are labor intensive, time consuming, costly, bulky and next to impossible to perform in congested areas. In such scenarios, the automated and modified version of Swedish Weight Sounding machine i.e., Screw Driving Sounding (SDS) can prove to be a savior. However, since the SDS machine was unable to explore stiffer and denser soil layers deep below, researchers customized the machine for research and increased the capacity of machine to explore soil profile in deeper depths using a high power SDS machine. This research has attempted to strengthen the prospects of SDS technique, by development of correlation formulae, which can predict various vital clay properties in Bangkok clay directly from SDS parameters. These clay properties are natural moisture content, unit weight, overburden and vertical effective stress. The study is focused on Bangkok subsoil, which is dominantly clay and a high power SDS machine is put into operation. It is observed that the results are highly dependent upon the history of formation of Bangkok clay. In order to represent the accuracy of the developed equations, various statistical parameters have also been used in this research and included in this paper.

Numerical Modeling of Single Pile Behaviors Due to Groundwater Level Rising

Behaviors of the pile foundation due to groundwater level rising were analyzed by a series two-dimensional finite element analyses with fully coupled flow-deformation analysis. The different numerical models of single bore pile depth and diameter in Bangkok subsoil were represented with the parametric study. The pile–soil movement due to groundwater levels rising between numerical simulation and a previous experiment of the centrifuge test as the same condition are in good agreement. With rising groundwater level, the reduction of pile capacity can be evidently performed by the increase of pile settlement relative to soil surface. Moreover, the development of the plastic point captured by the finite element analysis revealed the mechanism behind the reduction of pile capacity. In this study, the evaluation of pile stability due to groundwater level rising for preliminary guidelines to protect existing structures are proposed.

Optimization of deep soil mixing mass for construction of tunnel cross-passage in Bangkok

A cross-passage from a tunnel to an intervention shaft in Bangkok subsoils was modelled using three-dimensional finite element analysis. The optimization was performed for reducing the volume of soil-cement mass while maintaining ground stability. The result showed that the factor of safety increases linearly with the thickness of improved ground. The relationship between the improved groundmass and ground surface settlement curve was made. It was found that the predicted settlement profile can be captured by the formula proposed by Peck and O’Reilly, providing that the empirical coefficient of 0.6 is fit well with the results from the 3D simulation. This value was obtained from the average of empirical coefficient value 0.4 and 0.7, which are the empirical coefficient values of stiff clay and soft clay, respectively based on the overburden thickness.

NUMERICAL INVESTIGATION ON PILE BEHAVIOR DUE TO THE RISING GROUNDWATER EFFECT

Since the late 1990s, the changing of groundwater level in the aquifer beneath Bangkok has been realized because the enforcement of groundwater laws and improvement of water supply have been adopted. Then, the groundwater with piezometric drawdown has risen to almost hydrostatic equilibrium. In the principle of soil mechanics, when the porewater pressure in soil mass increases, the effective stress decreases. This can affect underground structures. Under the soft ground condition such as Bangkok, Thailand, pile foundations are commonly constructed to support structures. With decreased effective stresses, the loss of ultimate load-carrying capacity of existing piles can occur, and the structures can be damaged. This research investigates the effects of the groundwater rising on the pile foundation in the Bangkok subsoil. An advanced numerical model with the fully coupled flow deformation analysis, both groundwater flow and soil deformation behaviors with time-dependent conditions are modeled, is conducted by using PLAXIS 2D. The results found that the calculation type of fully coupled flow deformation can express the pile-soil movement behavior. The pile-soil heave and the pile load capacity be significantly reduced during the groundwater rising event. Despite the reduction of pile load capacity with groundwater changed not enough to failure (Factor of safety <1.0), the pile stability should be concerned, and the optimum groundwater level must be controlled.

Non-Linear Site Response Analysis of Bangkok Subsoils Due to Earthquakes Triggered by Three Pagodas Fault

Non-Linear Site Response Analysis of Bangkok Subsoils Due to Earthquakes Triggered by Three Pagodas Fault

Influence of the Spatial Variability of Soil Shear Strength on Deep Excavation: A Case Study of a Bangkok Underground MRT Station

This paper investigates the effects that the spatial variability of a soil's undrained shear strength has on lateral wall movements and ground surface settlements when performing a deep excavation stability analysis. A random finite-element method is employed to statistically assess a deep excavation. A case study based on an actual deep excavation project in Bangkok's subsoils was used to validate the methodology. The two-dimensional spatial variability of the undrained shear strength in the clay layers of Bangkok's subsoil is simulated using the random field theory and Monte Carlo simulation. The Mohr–Coulomb model is used to predict lateral wall movements and ground surface settlements, while the stability analysis of the deep excavation is evaluated by the factor of safety using the strength reduction approach. The results show that spatial variability highly affects the distribution of lateral wall movements and ground surface settlements, as well as the scatter of the factor of safety corresponding to progressing stages of excavation.

Influence of spatial variability of ground on seismic response analysis: a case study of Bangkok subsoils

The objective of this study was to observe the spatial variation in the geological subsoil condition on the seismic ground response of Bangkok subsoils during the remote 6.8 Mw Tarlay earthquake in 2011 in Northern Thailand. A simulation of random locations was initially performed to define the studied locations. The dynamic parameters, such as the soil index properties, shear modulus, and shear wave velocity, were determined from the subsurface modeling of Bangkok subsoils. Next-generation attenuation analysis was performed to define the input ground motion at each investigated site. Non-linear one-dimensional site response analysis was performed to investigate the surface ground motion, amplification factor, and spectral acceleration during short (0.2 s) and long (1 s) time periods. In general, it is important to consider the ground spatial variation in any seismic ground response analysis. The results show that Bangkok subsoils could magnify the seismic wave during an earthquake. For example, in the 2011 Tarlay earthquake, the magnification varied from two- to four-fold. The results from this study can be used to define the microzonation of the ground motion characteristic of Bangkok subsoils, such as the peak ground acceleration and the spectral acceleration, at short and long periods.

Comparison of diaphragm wall movement prediction and field performance for different construction techniques

The demand for deep excavation for basement construction is growing rapidly in Bangkok due to the limited availability of land. Recently, the maximum depth of excavation has increased up to approximately −25 m. Deep excavation in Bangkok subsoils requires consideration of the soil conditions and the real piezometric level of ground water. In general, Bangkok subsoil consists of 13~16 m of thick, dark grey soft-to-medium clay, followed by stiff, silty clay, before the first sand layer at 21~30 m. The piezometric level of ground water has risen to −13 m from its previous level of −23 m due to the control of deep well pumping for twenty years by the Thai Government. A diaphragm wall is normally used as a soil retaining structure. The behavior and performance of a diaphragm wall is usually predicted by the finite element method (FEM) using Mohr–Coulomb soil modeling as failure criteria, with the soil modulus parameters for soft and stiff Bangkok clay from the self-boring pressuremeter test. This paper presents a comparison between the diaphragm wall movements from FEM analysis predictions and field measurements for two projects, the new Bank of Thailand head office and the Rosewood Hotel, which were constructed with different techniques. The predicted movement agreed well with the field measurements.

Underground excavation behaviour in Bangkok using three-dimensional finite element method

This study provides evidence that three-dimensional finite element modelling can be effectively applied for deep excavation analysis in Bangkok. The Bangkok subsoils were modelled using the hardening soil model and their parameters were calibrated against the results of laboratory and field tests. A study of a MRT station excavation was initially used to validate the model. The predicted wall movements and surface settlements were compared with the instrument data and two-dimensional analysis from a previous study. Another deep excavation project was selected asan independent study. The result shows that the model can be confidently used for deep excavation analysis.

3-D NUMERICAL ANALYSIS OF CONSOLIDATION EFFECT ON PILED RAFT FOUNDATION IN BANGKOK SUBSOIL CONDITION

This study focused on the investigation of influencing factors on behaviour of piled raftfoundation in Bangkok subsoil. To evaluate the possibility of implementing this system in Bangkok subsoilcondition, this research performed the consolidation analysis of piled raft foundation systems for low-rise (8-storey) and high-rise (25-storey) buildings with basement levels in clay soil, using coupled three-dimensional(3D) mechanical and hydraulic numerical model. The soils are modelled with Hardening Soil model andMohr-Coulomb model. Evaluations of piled raft foundation, i.e., the load sharing ratio of piles, settlementbehaviours in the foundation system are performed. The parametric study on the effect of raft depth, and loadcarried by piles of piled raft was done. The consolidation had a strong influence on the load carried by pilesof the piled raft foundation in Bangkok. The load shared by piles can increase by up to 12% and 6% for lowrise and high-rise buildings, respectively due to the consolidation effect. Therefore, the design of the piledraft foundation system in Bangkok subsoil essentially consider the consolidation effect.

Undrained face stability of tunnels in Bangkok subsoils

This paper presents the analysis of undrained face stability of tunnels in Bangkok subsoils. In this study, two-dimensional (2D) and three-dimensional (3D) finite element analyses were employed to analyse the 2D plane strain conditions of transverse (2DT) and longitudinal (2DL) sections as well as the full 3D geometry, respectively. The simplified geometry of 2DT corresponds to the circular face of tunnels subjected to a uniform face pressure, while that of 2DL correspond to the plane strain heading applied by a uniform face pressure at the front plane. For the 2D plane strain transverse and longitudinal sections, the tunnel lining was not considered in the analyses. For 3D cases, tunnel linings were included in the analysis and modelled as the rigid plate element with the fully rough surface along their lengths, while the tunnel face was subjected a face pressure. For all cases, the uniform surcharge was applied all over the ground surface. Strength reduction methods in conjunction with 2D and 3D finite element analyses were employed to determine the stability and the factor of safety of this problem. The stability analyses included ranges of tunnel face pressure measured during the tunnelling process. Effects of three-dimensional stability of tunnel face were also presented and discussed in this paper. Results of analyses were verified and compared with existing methods.

Application of the Non-Destructive Testing Method to Determine the G&lt;sub&gt;max&lt;/sub&gt; of Bangkok Clay

This article presents the application of the non-destructive testing method (so called Bender element test) to measure the shear wave velocity and determine the maximum shear modulus of soft Bangkok clay samples. This research proposes the bender element technique to measure the shear wave velocity by means of piezoelectric ceramic sensors. The details of the bender element test were clearly explained. The laboratory bender element test data of the shear wave velocity were compared with the field test results and show that the field propagating waves pass along layers of higher stiffness while the laboratory test data were performed on small, possible less stiff material. The inversion calculation of the shear wave velocity in the field test is based on a linear elastic isotropic assumption which is not valid for the Bangkok subsoil and might be a second reason for the noticed differences in velocity.

Stiffness and strength parameters for hardening soil model of soft and stiff Bangkok clays

A comprehensive set of experimental data on Bangkok subsoils from oedometer and triaxial tests are analysed in this paper in order to determine the stiffness and strength parameters for Hardening Soil Model. The parameters determined are the Mohr–Coulomb effective stress strength parameters together with the stiffness parameters; tangent stiffness for primary oedometer loading, secant stiffness in undrained and drained triaxial tests, unloading/reloading stiffness and the power for stress level dependency of stiffness. The oedometer data are obtained from three different Bangkok soil layers: soft clay at 6–8m depths; medium clay at 12–14m depths; and stiff clay at 15.5–18m depths. The triaxial tests data are carried out for soft and stiff clays at depths of 5.5–6m and of 16–18m under both undrained and drained conditions, respectively. Finally, two sets of parameters for soft and stiff Bangkok clays are numerically calibrated against undrained and drained triaxial results using PLAXIS finite element software.

Assessment of tunnelling under existing mass rapid transit tunnel in Bangkok subsoil

Tunnelling under existing tunnels in Bangkok has been undertaken in recent years. Unfortunately, monitoring in the vacant tunnel is inapplicable as most tunnels are constructed for the Metropolitan Water Network. Hence, close investigation of any deformation has not been carried out and the deformation of existing tunnels in Bangkok geology is unknown. Only ground deformation directly around water supply tunnel was monitored in previous projects. However, the city is developing, so the underground space will become smaller. Therefore, tunnel construction may not be able to avoid such close interaction with the existing underground structure in the near future. This article presents a study of the deformation of the mass rapid transit (MRT) subway tunnel during the construction of new underneath diversion tunnels. Lining deformation of the existing MRT subway tunnel is discussed in connection with the performance of TBM operation, including face pressure, advance rate, grout pressure and volume loss. In ad...

Evaluation of ground movements in EPB-shield tunnelling for Bangkok MRT by 3D-numerical analysis

This paper presents results of 3D numerical analysis using FLAC3D to evaluate characteristics of ground movements associated with MRT subway tunnelling using EPB shields in Bangkok subsoils. Effects of influencing factors i.e. face pressure, soil layering, piezometric drawndown of groundwater, tail void grouting, and input values of initial horizontal ground stress were investigated. A comparison was made between the prediction by the analysis and monitoring data. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

Deep-well pumping in the Bangkok Plain and its influence on ground improvement development with surcharge and vertical drains

The Bangkok subsoil that forms part of the larger Chao Phraya Plain consists of a broad basin filled with sedimentary soil deposits that form alternate layers of sand, gravel and clay. The depth of the bedrock is still undetermined, but its level in the Bangkok area is known to vary between 400 m and 1800 m deep. The aquifer system beneath the city area is very complex, and the deep-well pumping from the aquifers over the last 50 years or so has caused substantial piezometric drawdown in the upper soft and highly compressible clay layer. In this paper, the influence of the piezometric drawdown on the performance of vertical drains with surcharge on the upper clay layer is examined. Instrumented test embankments were built and the performance of large-diameter sand drains, sand wicks and prefabricated vertical drains was examined. A novel interpretation technique was adopted to evaluate the settlements from pore pressure dissipation and to compare with those measured directly from settlement measurements. Le sous-sol de Bangkok qui forme une partie de la plaine plus vaste de Chao Phraya est constitué d'un large bassin rempli de dépô ts sédimentaires qui forment des couches alternées de sable, de gravier et d'argile. La profondeur du lit rocheux reste indéterminée mais on sait que son niveau dans la zone de Bangkok se situe entre 400 m et 1800 m de profondeur. Le système aquifère sous la ville est très complexe et un pompage à puits profonds au cours des 50 dernières années a causé une baisse substantielle du niveau piézométrique dans la couche argileuse supérieure molle et hautement compressible. Dans cet exposé, nous examinons l'influence de la baisse piézométrique sur la performance de drains verticaux surchargés sur la couche argileuse supérieure. Des berges de contrôle instrumentées ont é té construites et la performance de drains de sable de gros diamètre, de mèches de sable et de drains verticaux préfabriqués a été é tudiée. Nous avons adopté une technique d'interprétation innovante pour é valuer les tassements d'après la dissipation de la pression interstitielle et pour les mesures de tassement directes.

Development of negative skin friction on driven piles in soft Bangkok clay: Reply

This paper describes the results of short-term pullout tests and long-term full-scale measurements of negative skin friction on driven piles in Bangkok subsoils. Two instrumented cylindrical (hollow) prestressed concrete piles were fully equipped with two independent load-measurement systems, load cells, and telltale rods. Pore pressures and ground movements in the vicinity of the piles were monitored throughout the period of investigation. The effect of bitumen coating on negative skin friction was also studied. The long-term behaviour of driven piles was compared with the estimated values obtained from short-term pullout tests and soil strength data. It was found that the negative skin friction can be predicted well by the effective stress approach using values of β between 0.1 and 0.2. The load–settlement and load–transfer behaviour were numerically modelled to acquire a more comprehensive understanding of negative skin friction developed on driven piles. A settlement-controlled concept is also introdu...

Development of negative skin friction on driven piles in soft Bangkok clay

This paper describes the results of short-term pullout tests and long-term full-scale measurements of negative skin friction on driven piles in Bangkok subsoils. Two instrumented cylindrical (hollow) prestressed concrete piles were fully equipped with two independent load-measurement systems, load cells, and telltale rods. Pore pressures and ground movements in the vicinity of the piles were monitored throughout the period of investigation. The effect of bitumen coating on negative skin friction was also studied. The long-term behaviour of driven piles was compared with the estimated values obtained from short-term pullout tests and soil strength data. It was found that the negative skin friction can be predicted well by the effective stress approach using values of β between 0.1 and 0.2. The load–settlement and load–transfer behaviour were numerically modelled to acquire a more comprehensive understanding of negative skin friction developed on driven piles. A settlement-controlled concept is also introduced for piles subjected to negative skin friction, on the basis of these findings. Key words : consolidation, downdrag, driven pile, embankment, finite elements, pore pressures, pullout, settlements, soft clay.

Settlements of structures and their predictions in Bangkok subsoils : Sambhandharaksa, S; Pongrujidorn, T; Chaloeywares, P Proc ninth southeast asian geotechnical conference, Bangkok, 7–11 December 1987V1, P4.25–4.40. Publ Bangkok: Southeast Asian Geotechnical Society, 1987

Settlements of structures and their predictions in Bangkok subsoils : Sambhandharaksa, S; Pongrujidorn, T; Chaloeywares, P Proc ninth southeast asian geotechnical conference, Bangkok, 7–11 December 1987V1, P4.25–4.40. Publ Bangkok: Southeast Asian Geotechnical Society, 1987