Abstract
Monitoring surface movement near highways over soft clay subgrades is fundamental for understanding the dynamics of the settlement process and preventing hazards. Earlier studies have demonstrated the accuracy and cost-effectiveness of using time series radar interferometry (InSAR) technique to measure the ground deformation. However, the accuracy of the advanced differential InSAR techniques, including short baseline subset (SBAS) InSAR, is limited by the temporal deformation models used. In this study, a comparison of four widely used time series deformation models in InSAR, namely Multi Velocity Model (MVM), Permanent Velocity Model (PVM), Seasonal Model (SM) and Cubic Polynomial Model (CPM), was conducted to measure the long-term ground deformation after the construction of road embankment over soft clay subgrade. SBAS-InSAR technique with TerraSAR-X satellite imagery were conducted to generate the time series deformation data over the studied highway. In the experiments, three accuracy indices were applied to show the residual phase, mean temporal coherence and the RMS of high-pass deformation, respectively. In addition, the derived time series deformation maps of the highway based on the four selected models and 17 TerraSAR-X images acquired from June 2014 to November 2015 were compared. The leveling data was also used to validate the experimental results. Our results suggested the Seasonal Model is the most suitable model for the selected study site. Consequently, we analyzed two bridges in detail and three single points distributed near the highway. Compared with the ground leveling deformation measurements and results of other models, SM showed better consistency, with the accuracy of deformation to be ±7 mm.
Highlights
The stability management of soft clay subgrade, is one of the main challenges in the field of highway engineering [1,2]
The reason is that Permanent Velocity Model (PVM) does not incorporate the nonlinearity of the deformation in the process of modeling, which may cause greater modelling error if nonlinearity exists; Cubic Polynomial Model (CPM) improves the accuracy by suppressing the fitting error, if the real deformation sequences do not follow the temporal 3rd order polynomial function, the estimated time series of deformation may be incorrect
After our comparative model analysis, we carried out seasonal time series deformation investigations based on Seasonal Model (SM) over the test highway area
Summary
The stability management of soft clay subgrade, is one of the main challenges in the field of highway engineering [1,2]. The potential of MTInSAR techniques [15], such as Permanent Scatterer Interferometry (PSInSAR) [16,17], Small Baseline Subset (SBAS) [18,19], and Temporally Coherent Point InSAR (TCP-InSAR) [20,21], etc, have been investigated for measuring time-series ground deformation over man-made infrastructures, such as railways, highways and bridges [22,23,24,25] Those high coherence points can keep long-term stable back scatter characteristics over multi-SAR images, which cannot be affected by spatial-temporal decorrelation [26]. MTInSAR can detect ground displacement information with millimeter precision, showing high potential ability for application to large traffic infrastructures [27]
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