Refined InSAR Mapping Based on Improved Tropospheric Delay Correction Method for Automatic Identification of Wide-Area Potential Landslides

Slow-moving landslides often occur in areas of high relief, which are significantly affected by tropospheric delay. In general, tropospheric delay correction methods in the synthetic-aperture radar interferometry (InSAR) field can be broadly divided into those based on external auxiliary information and those based on traditional empirical models. External auxiliary information is hindered by the low spatial–temporal resolution. Traditional empirical models can be adaptable for the spatial heterogeneity of tropospheric delay, but are limited by preset window sizes and models. In this regard, this paper proposes an improved tropospheric delay correction method based on the multivariable move-window variation model (MMVM) to adaptively determine the window size and the empirical model. Considering topography and surface deformation, the MMVM uses multivariate variogram models with iterative weight to determine the window size and model, and uses the Levenberg–Marquardt (LM) algorithm to enhance convergence speed and robustness. The high-precision surface deformation is then derived. Combined with hotspot analysis (HSA), wide-area potential landslides can be automatically identified. The reservoir area of the Baihetan hydropower station in the lower reaches of the Jinsha River was selected as the study area, using 118 Sentinel-1A images to compare with four methods in three aspects: corrected interferograms, derived deformation rate, and stability of time-series deformation. In terms of mean standard deviation, the MMVM achieved the lowest value for the unwrapped phase in the non-deformed areas, representing a reduction of 56.4% compared to the original value. Finally, 32 landslides were identified, 16 of which posed a threat to nearby villages. The experimental results demonstrate the superiority of the proposed method and provide support to disaster investigation departments

Macro and micro analysis on deformation characteristics of fine sand under different groundwater table change

By using the samples of fine sand in Shanghai’s seventh layer, creep tests were performed to investigate the deformation characteristics of fine sand under different groundwater table change. It was revealed that the creep of fine sand is closely related to groundwater table change: when the effective force caused by groundwater table change is smaller than pre-consolidation force, the deformation is mainly elastic. When effective force caused by groundwater table change is bigger than pre-consolidation force, the compression deformation is large and the rebound is small; and the deformation is mainly viscoelastic plastic when equal to pre-consolidation stress. Through the scanning electron microscope (SEM) analysis it was found that creep of fine sand is dominated by the slip of particles, not by the breaking of particles. And the fine sand particles are squeezed under the load induced by the groundwater table change, and the particles slide along the indirect contact surface of the particles, resulting in the continuous adjustment of position and relative displacement. Mercury injection test shows that the pore size distribution of fine sand has little change before and after the test

Road Performance and Emission Reduction Effect of Graphene/Tourmaline-Composite-Modified Asphalt

The purpose of this study is to further improve the road performance and emission reduction effect of tourmaline-modified asphalt. Graphene was used to enhance the performance of tourmaline-modified asphalt, and graphene/tourmaline-composite-modified asphalt was prepared. The temperature susceptibility, high temperature, anti-aging properties and rheological performance of the modified asphalt were studied. The test method of emission reduction efficiency of the modified asphalt and its mixture was proposed. The emission reduction effect of different modified asphalts and its mixture was evaluated. The enhancement effect of graphene on the properties of tourmaline-modified asphalt was confirmed. It provides a reference for the performance enhancement of inorganic material modified asphalt. The results show that the temperature susceptibility, high temperature, anti-aging properties and rheological performance of the graphene/tourmaline-composite-modified asphalt are better than those of the tourmaline-modified asphalt and base asphalt. The asphalt fume reduction rate of graphene/tourmaline-composite-modified asphalt is higher than that of tourmaline-modified asphalt. With the increase of graphene content, the emission reduction performance increases gradually, and the enhancement effect of graphene on tourmaline performance is more obvious