Construct and evaluate the classification models of six types of geological hazards in Bijie city, Guizhou province, China

Debris flow, landslide, ground collapse, collapse and ground collapse are the dominating geological hazards in Bijie city, Guizhou province, which is situated in the area with high natural hazards in China. The primary purpose of this study is to construct different classification models by using the disaster conditioning factors of geological hazards and to evaluate the performance of the models in the classification of geological hazards in Bijie city. At the same time, the nonlinear relationship between various geological hazards and conditioning factors will be discussed. Firstly, the manual field survey data of Bijie city in 2019 were applied to construct and draw inventory map of six geological hazards. Then 16 conditioning factors were established from various data sources. According to the ratio of 70:30, the geological hazard location points were randomly divided into the training and validation set to complete the training and verification process of the classification models. In order to select the optimal subset of the conditioning factors, the multicollinearity of these factors was assessed using tolerances and variance inflation factors(VIF) and Pearson’s correlation coefficient, and factors with multicollinearity were excluded to optimize the model. Subsequently, ten classification models were structured, and the models were verified and compared by using the receiver operating characteristic(ROC), precision, sensitivity, Kappa coefficient and F1 values.In addition, the Friedman test was used to identify statistically significant differences between the results of the classification model used in this research. In general, average Area Under Curve (AUC) values under the ROC curves of the 10 classification models is above 0.8, indicating that all models have a corresponding high prediction ability. Among them, the average AUC value(0.941), AUC values for individual geological hazards (collapse: 0.949, ground crack: 0.907, ground collapse: 0.952, landslide: 0.830, displacement flow: 0.963, slope: 0.922), Kappa coefficient (0.845), Macro F1(0.851) and Micro F1(0.878) of SVM all had the highest values.

Stability Analysis of Soft Soil Foundation Excavation of Underground Station in Coastal Area of Tianjin

The marine sedimentary strata are spread in coastal area of Tianjin. Due to low soil strength, high underground water level and strong soil plasticity flow, instability accidents happened frequently in soft soil area. In the foundation excavation of underground station, because of stress release and change in ground water level, the differential settlement of surrounding buildings, ground crack and deformation of underground pipeline will happen. The stability of surrounding rocks in the foundation excavation of underground station has been calculated and analyzed by using numerical simulation method. The Surrounding soil deformation of foundation pit has been gotten to analyze.

Research on the Impact of Ground Crack on Soil Nitrogen in Sandy Area Pit Mining

The ground cracks caused by mine activities lead to soil destruction in sandy area. Most of the previous literatures focus on the soil properties change before and after the large area subsidence, and the research of the ground crack impact on soil are inadequate. This paper takes the soil around the static cracks as the research object, analyzes the impact law of the soil total nitrogen by using the comparative analysis method. The impact law and impact range of the soil total nitrogen by ground crack, and the impact mechanism of the soil porosity and soil particle size, are analyzed. The result show that: within 200cm away from static cracks, the soil total nitrogen content is decreases in the close distance, increases in the middle, and keeps gentle change in the long distance; The effect boundary of the total nitrogen by static cracks is about 100cm, providing information for further study on the soil quality influenced by coal mining in the sandy area.

Geohazard Forecasting in Mining Area Based on Grey Model

This paper studied a forecasting method of geological hazard in loess plateau mining area, by making use of a grey system theory and building grey model, it is expected that in 2018, the loss statistics of mining geology hazard in the area will increase steadily, the loss of water-inrush, slag, ground subsidence, landslide collapse and ground crack will reach relatively 623,480 dollars, 879,346 dollars, 75.833 km2/103km2, 811.295*104m3, 597,761 dollars in 2018. The prediction results provided geological bases for the economic and social sustainable development, ecological environment construction and protection.