Is it difficult? Textbooks suggest that it is easy. Find, assess or measure some compressibility parameters, predict stress increase due to the applied load, and carry out some simple calculations. But how often do we get a chance to check that our calculations provide a representative result?
The Muar Trial Embankment, built in Malaysia as part of the geotechnical investigations for the North-South Expressway in 1988, has provided such an opportunity. In 2022 an International Symposium on “Practical Applications of Ground Engineering for Embankments on Soft Soil” was held in Kuala Lumpur, which included a competition to predict the settlement of two control embankments built as part of the 1988 trial.
The predictors were provided with the full site investigation information and the recorded settlement data for the first 3.5 years from the start of construction and then required to predict settlement after 33 years. The predictors used a variety of methods to calculate settlement, but the results were generally far from correct.
This talk will summarise the performance of the Muar Trial Embankment controls, as well as the predicted performance. Site investigation data available at the time of the construction of the trial will be examined, with the aim of establishing which parameters and assumptions are of greatest relevance to providing an accurate prediction of long-term settlement.
It will be seen that simple calculations can provide reasonable predictions, provided that the input parameters are representative. The parameter of greatest importance is the preconsolidation pressure, which will be examined in detail. The simple conclusion is that high quality site investigation and testing is essential when considering the question above.
