Volume 8, Issue 1

March 2023

Case History
Pa Sak River Improvement Project in Thailand
Hiroki Kitamura
Giken Seisakusho Asia Pte., Ltd.
Introduction
Climate change has become a serious problem worldwide. The number of reported natural disasters from 2000 to 2019
totaled 7,348, which was 1.7 times larger than the number of reported natural disasters from 1980 to 1999. Meanwhile,
44% of the total disasters from 2000 to 2019 were floods. (United Nations Office for Disaster Risk Reduction, 2020) In
2011, Thailand was devastated by a flood, where the total damage and losses amounted to THB 1.43 trillion (World Bank,
2012). It was reported that the flood was one of the worst floods in the modern Thailand history. To cope with increased
precipitation due to climate change, the Thailand government has implemented some flood protection measures. This
report introduces a case study of flood protection for the Pa Sak River in Ayutthaya.

Project Overview
The Pa Sak River is located in the northern area ofAyutthaya, as shown Fig. 1. It is extremely important forlogistics, which spans from the northern area of Thailand
to the industrial area of Ayutthaya. Furthermore, it isconnected to the Chao Phraya River, which flows throughBangkok to the sea. Local people use the Pa Sak River for
not only transporting industrial materials, but also fordaily transportation. This project involves improving thePa Sak River revetment, which spans 52km. One of thepurposes of this project is to prevent flood and excavate
the riverbed for larger cargo boats to ensure theappropriate navigation. New revetments such as sheet
pile walls can prevent the riverbanks from collapsingwhen the riverbed is excavated as well as from erosion
via flash floodings and waves generated by large cargoboats.

Fig. 1. The map of Pa Sak River ProjectⒸOpenStreetMap contributors(https://www.openstreetmap.org,https://opendatacommons.org)

Phase 1 of the project commenced in 2015 and was completed in 2019. In Phase 1, a U-shaped steel sheet pile wall anda concrete wall were utilized as flood protection, as shown in Fig. 2. Currently, Phase 2, which began in 2021, is now inprogress and will be completed in 2025.

Fig. 2. U-shaped sheet pile revetment in Phase 1
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Structural TypeThe project (specifically Part 1 of Phase 2) is the first in Thailand to adopt SILENT PILERTM F301-900 and hat-type steel
sheet piles. Hat-type sheet piles were utilized as a revetment and they were used to form a double hat-type sheet pilewall, as shown in Figs. 3 and 4. The hat-type sheet pile offers some advantages, one of which is its width. The width of a
hat-type sheet pile is 900 mm, which is 2.25 times greater than that of a U-shaped 400 mm sheet pile. Therefore, thetotal number of sheet piles to be used can be reduced. In other words, the construction period can be shortened,particularly in soft ground. The other advantage is no consideration of a reduction factor in design stage. The hat-typesheet pile does not require the consideration of a reduction factor as the interlocking position is not located on the centerline of the sheet pile wall. Therefore, the total weight of a sheet pile wall is less than that of a U-shaped sheet pile.

Fig. 3. Cross section of hat-type sheet pile wall
In this project, 45H and 25H hat-type sheet piles were utilized on
the riverside and landside respectively. The total number of sheet
piles installed at those locations was 4,238. In addition, 2,797 of
the 4,238 were installed using SILENT PILER F301-900 to ensure
accuracy as they must be placed adjacent to residential areas.
After the hat-type sheet piles were installed, excavation wasperformed to allow large vessels to be operated on the Pa Sak
River. To serve the community, the top of the sheet pile was laidwith a concrete slab to function as a road for pedestrians.
Moreover, stairs on the riverside allowed the locals to use theirboats for crossing the river as a means of transportation. Thesheet pile wall, which comprises sidewalks and stairs, improves
the living environment of the local residents and eliminates thefear of floods.
14Fig. 4. Double hat-type sheet pile wallVolume 8, Issue 1

March 2023

Press-in Piling Method
As shown in Fig. 5, the SPT N value of this project is approximately 50. Therefore, the press-in with water jetting method(water jetting mode) was adopted. Water jetting is one of the press-in penetration technologies. Press-in with water
jetting can reduce the penetration resistance force efficiently. High-pressure water jetting can increase the porewaterpressure between soil particles and allow them to easily propagate temporarily. In addition, water that is approaching
the ground can reduce the skin friction of the piles and interlock resistance by removing the soil between the interlocks.
Consequently, the piles can be installed using the minimum press-in force. Driving assistance such as water jetting is
critical for preventing damage to the piles. Figs. 6 and 7 show the main components of the water jetting mode and aphotograph of the Pa Sak River project. The main components comprised a press-in machine with JET REELTM, a power
unit, a water jet pump, a water tank, a generator, and a water pump.

Water Jet Pump
Generator

Power Unit

JET REELTM

TankPress-inMachine

Water Pump

Fig. 6. Main components of water jetting mode

Fig. 5. Borehole data

Fig. 7. Photograph of Pa Sak River(Generator is behind the power unit and water pump is on the riverside)

Fig. 8 shows the details of the equipment, and Fig. 9 shows thepress-in with water jetting process. The most significant
difference in the standard press-in process is indicated whencomparing between Steps 2 and 7, which primarily involve theJET REEL and PILER ECOTM Hose, respectively. The reel is used towind the hose. The hose is wound up and unreeled automaticallyby the reel. In Step 2, the jet nozzle is inserted into the JET
LOCKTM, which is welded on the pile and locked by the pin. InStep 7, after the pile is installed, the hose is extracted by the reel.
Therefore, the PILER ECO Hose can be utilized repeatedly.

15PILER ECOTM
HoseJet Nozzle
JET LOCKTMLock Pin

Fig. 8. Water jetting equipment

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Fig. 9. Construction process
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Among the various reasons, the Press-in Method was adopted owing to its environmental friendliness. The press-inmachine emits minimal noise and is almost vibration-free. Therefore, it can be applied adjacent to residential areas, as
shown in Fig. 10. The other reason is the highly accurate installation afforded by the method. The press-in machine grips
the sheet pile near the ground, thus allowing the appropriate amount of press-in force to be transmitted to the pile.
Consequently, the alignment and verticality achieved are extremely accurate. In this project, hat-type sheet piles wereused as permanent structures. Therefore, the completed shape is critical.

Fig. 10. Construction performed adjacent to buildings

Conclusion
A case study of the Pa Sak River improvement was introduced herein. It is the first project that adopted SILENT PILER
F301-900 and the hat-type sheet pile in Thailand, which has demonstrated some advantages. For instance, the Press-inMethod adopted, which is low in noise and vibration, can minimize adverse effects to the environment. The hat-type
sheet pile, which features a width of 900 mm, affords a shorter construction period. Owing to climate change, natural
disasters such as heavy rains, typhoons and hurricanes are expected to increase in the future. In addition, the increasing
sea level is a critical issue. In Thailand, both coastal and flood protection must be implemented to ensure the safety ofthe public. We strongly believe that the Press-in Method can mitigate the above-mentioned issues.

References
United Nations Office for Disaster Risk Reduction. 2020. Human Cost of Disasters An Overview of the Last 20 Years 2000
2019. pp.6-7. https://doi.org/10.18356/79b92774-en (accessed 16-December-2022).
World Bank. 2012. Thai Flood 2011 Rapid Assessment for Resilient Recovery and Reconstruction Planning. p.2.
https://doi.org/10.1596/26862 (accessed 16-December-2022).

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