The overall dissolution and weathering of limestone slope have significant temporal and spatial variability, so it is difficult to obtain the mechanical parameters of complete slope accurately and effectively according to conventional specifications, and the reliability of the numerical simulation result would be weaken or even to be completely invalid, and it is difficult to provide effective reference information for field construction. Therefore, a method for obtaining the mechanical parameters of slope based on GPR and displacement back analysis is proposed. On the basis of a limestone slope in No. 2 section of Yizhou-Hechi expressway in Guangxi, the water-rich and crushing properties of the slope are detected by GPR, and the slope is divided into different graded units. Then, a displacement gauge is installed on the non-cavity unit block to measure the displacement value of the unit block, and the mechanical parameters such as elastic modulus, poison's ratio and cohesive force of different unit blocks are obtained by using BMP90 displacement back analysis method accordingly. The grid model of complete slope is established by using MIDAS-GTS finite element numerical simulation software, and the sliding displacement value of the slope is calculated by using the mechanical parameters of different unit blocks obtained by back analysis and the whole assignment of specification. In order to compare and verify the numerical simulation result of the sliding displacement value, the field synchronous monitoring and measurement of the displacement is carried out. Compared with the results of synchronous field displacement monitoring and measurement, it is found that the numerical simulation values based on slope unit division and its back analysis result are close to the monitored values, which indicates that the mechanical parameters obtained by this method are more consistent with the real values of slope than the mechanical parameters of complete slope generally assigned according to the specification. The study can provide relevant reference for numerical simulation analysis of limestone slope stability in dissolved areas.

To accurately obtain the waveform and spectral characteristics of saline soil subgrade, on the basis of the provincial highway widening project of Ruoqiang-Weili county in Sinkiang, the field detection of coarse-grained weak sulfuric acid saline soil subgrade was carried out by using the type LTD-2100 ground-penetrating radar (GPR) to obtain the original measured files under different water content (ω) levels. IDSP analysis program was used to process the measured file and obtain the initial characteristics of waveform and frequency spectrum. To verify the initial characteristics, a rectangular model box was created in the laboratory with the field packing (the size was 1×0.8×0.8 m), and the water content of the model packing and temperature were manually adjusted. The model property of the waveform and frequency spectrum was obtained by detecting the model. A comparison of the initial property with the model property shows that under a positive temperature, the increase in ω will enhance the electromagnetic reflection, and when 8% < ω < 27%, the reflection amplitude reaches the maximum, the maximum normalized amplitude is close to 1.0, the spectrum energy is dispersed, and the main frequency is not critical while it is lower than 200 MHz. When ω > 32%, the electromagnetic loss is significantly intensified as the line mapping shows typical snowflake-like characteristics, and the point mapping shows typical linear characteristics, the spectrum energy is concentrated, the main frequency distribution range is 20-65 MHz, and the low frequency characteristics are evident. The results can provide a relevant reference for GPR detection and interpretation of coarse-grained weak sulfuric acid saline soil subgrade.