Numerical Simulation of Long-term Peat Settlement Under the Sand Embankment

Abstract

Long-term surface settlement in the cities, which were founded in swamp lands, is a reason of road pavement, underground pipelines, building damage. One of such cities is Arkhangelsk, which was founded on the swamp with peat thickness of 4-6 meters and even 8 meters. In such difficult geological conditions, the prediction of long-term settlements of a peat layer under an embankment is the significant task. One of the contemporary and effective ways of its solution is numerical simulation. The numerical simulation was performed using the software PLAXIS. The model of Soft Soil Creep was used.The objective of this project was comparing the long-term peat settlement values by way of numerical simulation, using the results of peat compression tests as initial data, with the data of monitoring. Thus, we can say about the model verification.On the first step of the research input parameters λ*, μ* were received from the laboratory tests data according to the basic methods. After that numerical simulation of oedometer tests was done. The small disarrangement between calculated settlement-in-time plots and the oedometer test data showed that that the SSC model gives an adequate representation of the physical processes in the peat specimen.On the second step, we simulated the experimental field, which settlement data has being collected more than 23 years. During this period, peat settlement was 1.4-4 m, depending on the thickness of the sand embankment. Input parameters λ*, μ* from the oedometer test were used. The comparison showed the low level of convergence of the settlement-in-time plots with the field data, so the model parameters calibration was required. The correction factors were to be added to the parameters λ* and μ* calculated by the results of oedometer tests.