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This study developed a discrete element simulation model based on the 2D particle flow code (PFC2D), of which the mesoscopic parameters were calibrated by the indoor experiments, to investigate the rainfall erosion damage of residual soil slope in the intermittently frozen area. It is to be noted that the runoff scouring action was simulated according to the equivalent rainfall method, the soil particles on the slope were given initial velocity, and the water absorption was considered by increasing the unit weight. The results indicated that the scouring action only caused superficial erosion with the main damage region at the foot, regardless of the FT effect. A splitting phenomenon was observed in the lower part of the steeper slope under the FT effect. Moreover, regardless of the FT effect, the gentler slope tended to incur spalling rather than a splitting phenomenon, where the soil particles slid along the structural plane with strong anti-scouring ability. Besides, the gentler slope maintained higher stability and shorter scouring time. Finally, the scouring velocity increased the erosion damage to a large extent.

The in situ frost-heaving (FH) process and characteristics of the shallow layer of a residual soil slope in the intermittently frozen zone were simulated by a modified three-dimensional particle flow code (PFC3D) model, of which the mesoscopic parameters of soil and ice particles were calibrated through the indoor experiments. In this model, the in situ FH process was gradually achieved by expanding the volume of ice particles (divided into 24 times of expansion), and the process was terminated when the monitored porosity was stable. These countermeasures avoided the stress accumulation and effectively realized the simulation of the in situ FH process. The results found that the displacement occurred firstly and got the largest final value at the surface angle (SA) under the in situ FH effect, followed by that at the foot, and it gradually extended to the interior based on these two regions. The vertical tension was present at the SA, and the major force type in the lateral interlayer was pressure. In addition, the FH effect seemed to be strongly related to the frozen depth, and a sliding surface was found in a steeper slope. Finally, the smaller stone appeared to be favorable to the slope stability, but it was reduced by the larger stone to some extent.

This paper investigates three approaches for detecting the content of styrene-butadiene-styrene (SBS) in its modified asphalt. The physical, rheological, and structural analysis are respectively conducted by the conventional tests, dynamic shear rheology, and Fourier transform infrared spectroscopy (FTIR) tests. The results show that the fitting coefficient of the quadratic equation between the SBS content and viscosity or softening point or phase angle is very high, but these tests are time-consuming. The absorption peak at 966 cm-1 (the absorption peak area of 966 cm-1 is marked as A966, the same below) is selected as the characteristic peak of SBS, and the absorption peaks of 1377 cm-1, 811 cm-1 and 749 cm-1 are selected as the characteristic peak of the base asphalt in SBS modified asphalt. Comparing the applicability, accuracy and sensitivity of A966/A1377, A966/A811, and A966/A749, it is found that A966/A811 is more suitable as the indicator to determine the content of SBS. FTIR can realize the rapid and accurate detection of SBS content. Furthermore, A966/A811 has a good quadratic relationship with the performance of the modified asphalt.