Mobilized lateral earth pressure coefficient (Kmob) in peat under staged road embankment loading

¹ Department of Civil Engineering, Universiti Malaya, Kuala Lumpur, Malaysia
² Department of Civil Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Malaysia
³ Sarawak Public Works Department, Kuching, Malaysia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This paper presents a preliminary analysis of the mobilized lateral earth pressure coefficient (Kmob) of peat under staged road embankment loading. Data were obtained from a Category 5 rural primary road (R5) project in Malaysia using a novel Subsurface Sensor Module (SSM). The SSM integrates orthogonally installed earth pressure cells, a piezometer, and a settlement gauge within the central peat layer, providing high-frequency digital measurements at 10-minute intervals. These data are complemented by manual settlement plate measurements, inclinometer readings, and extensometer data. In this study, Kmob is defined as the mobilized ratio of effective horizontal stress to effective vertical stress beneath the embankment centerline. Findings reveal that Kmob is not bounded between Ka and Kp as conventionally assumed; instead, it originates in an unstable state (Kmob<Ka), evolves through Ka and Ko, and ultimately trends toward Kp. Observations beneath the centerline indicate that the peat undergoes lateral strain; thus deviating from the pure Ko compression conditions typical of standard oedometer testing. Instead, Kmob follows a specific stress-path-dictated evolution spanning Ka to Ko before transitioning into a passive loading state where Kmob approaches Kp. Results indicate that monitoring Kmob serves as a critical real-time indicator of embankment stability. This approach allows engineers to optimize construction protocols regarding filling sequences and rest periods, thereby enhancing efficiency and timelines. Integrating stress sensors with standard instrumentation provides the high-fidelity data necessary for rigorous analysis and field management. These findings offer valuable insights for the optimal design of road embankments on peat.