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Geomechanics and Engineering
  Volume 35, Number 5, December10 2023 , pages 511-523

 open access

The thickness of the soft soil layer and canal-side road failure: A case study in Phra Nakhon Si Ayutthaya province, Thailand
Salisa Chaiyaput, Taweephong Suksawat, Lindung Zalbuin Mase, Motohiro Sugiyama and Jiratchaya Ayawanna

    Canal-side roads frequently collapse due to an unexpectedly greater soft-clay thickness with a rapid drawdown situation. This causes annually increased repair and reconstruction costs. This paper aims to explore the effect of soft-clay thickness on the failure in the canal-side road in the case study of Phra Nakhon Si Ayutthaya rural road no. 1043 (AY. 1043). Before the actual construction, a field vane shear test was performed to determine the undrained shear strength and identify the thickness of the soft clay at the AY. 1043 area. After establishing the usability of AY. 1043, the resistivity survey method was used to evaluate the thickness of the soft clay layer at the failure zone. The screw driving sounding test was used to evaluate the undrained shear strength for the road structure with a medium-stiff clay layer at the failure zone for applying to the numerical model. This model was simulated to confirm the effect of soft-clay thickness on the failure of the canal-side road. The monitoring and testing results showed the tendency of rapid drawdown failure when the canal-side road was located on > 9 m thick of soft clay with a sensitivity > 4.5. The result indicates that the combination of resistivity survey and field vane shear test can be successfully used to inspect the soft-clay thickness and sensitivity before construction. The preliminary design for preventing failure or improving the stability of the canal-side road should be considered before construction under the critical thickness and sensitivity values of the soft clay.
Key Words
    sensitive clay; slope stability; soft clay thickness; rapid drawdown; road collapse
Salisa Chaiyaput: Department of Civil Engineering, School of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand
Taweephong Suksawat: Bureau of Testing, Research and Development, Department of Rural Roads, Bangkok 10220, Thailand
Lindung Zalbuin Mase: Department of Civil Engineering, Faculty of Engineering, University of Bengkulu, Bengkulu 38371, Indonesia
Motohiro Sugiyama: Department of Civil Engineering, School of Architecture and Urban Planning, Tokai University, Hiratsuka Kanagawa 259-1292, Japan
Jiratchaya Ayawanna: School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

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