Gongcheng Kexue Yu Jishu/Advanced Engineering Science

Chloride erosion is the most important factor affecting the corrosion of steel bars in the marine environment, salt lakes and saline soil areas. Therefore, timely and accurate grasp of the distribution of chloride ions inside reinforced concrete structures is of great significance to the durability evaluation, protection and repair of reinforced concrete structures under severe environmental conditions. In this paper, a solid Mn/MnO2 reference electrode for concrete with compact structure and stable performance is prepared by physical powder compaction method. The results show that the loading pressure is an important parameter that affects the strength and density of the Mn/MnO2 electrode prepared by the tablet method. When preparing Mn/MnO2 electrodes, the loading pressure needs to be controlled, and the recommended loading pressure is 96 MPa. The electrode must be activated before use. The response time of the activated Mn/MnO2 electrode is less than 60 s, and the stability, reproducibility and anti-polarization performance are good. When the Mn/MnO2 electrode works in the temperature range of 5~65 °C, the electrode potential is linearly related to the temperature. When the Mn/MnO2 electrode works in the pH range of 8.36~13.00, the electrode potential remains constant. Therefore, if the Mn/MnO2 electrode prepared by this method is used as the reference electrode of the chloride ion sensor to be buried in concrete, the temperature inside the concrete must be tested and corrected at the same time. Keywords: reference electrode; powder compaction method; performance characterization; influencing factors.

The experiment focused on the absorption and drainage characteristics of recycled coarse aggregate. The recycled coarse aggregate bonded with strain gauges was embedded in C30 strength grade concrete, and the shrinkage strain of recycled coarse aggregate in concrete during drying shrinkage was measured directly. Based on the relationship between the strain and drainage rate of recycled coarse aggregate under different humidity conditions, the drainage characteristics of recycled coarse aggregate in concrete were calculated, and the relationship between the drainage rate of recycled coarse aggregate and the drainage rate of recycled coarse aggregate was established. The results showed that the trend line of strain and saturation curve of regenerated coarse aggregate was relatively close to that of natural coarse aggregate in the process of draining and drainage, and the strain variation caused by dry and wet of the two kinds of aggregate had a reversible trend. There was a linear relationship between the strain and the drainage rate of recycled coarse aggregate and natural aggregate. The shrinkage strain of coarse aggregate in concrete was smaller than that of specimen, and the shrinkage strains of recycled coarse aggregate and recycled concrete were larger than that of natural aggregate and concrete. The drainage rate of recycled concrete was higher than that of internal recycled coarse aggregate.

Infiltration and groundwater have been widely considered as the main factors that cause shallow landslides; however, the effect of runoff has received less attention. In this study, an in-house physical-process-based shallow landslide model is developed to demonstrate the influence of runoff. The model is controlled by coupling the shallow water equation (dynamic) and Richards’ equation. An infinite slope stability analysis is applied to evaluate the possibility of regional landslides. A real, small catchment topography is adopted as a demonstration example. The simulation illustrates the variations of runoff and the factor of safety (FS) during a storm. The results indicate that, after the surface becomes saturated, the FS may keep varying due to the increasing pressure head, which is caused by increasing surface water depth. This phenomenon most likely occurs downstream where the slopes easily accumulate water. The depth of the surface water may also be a factor of slope failure. Therefore, it is essential to increase the accuracy of calculating the runoff depth when assessing regional shallow landslides.

The erodibility parameters of barrier dam were an important basis for the evaluation of the outburst flood in the emergency treatment of the dammed lake. The erosion rate was typically modeled with excess shear stress model and Wilson model. However, there is no unified understanding of the range of erodibility parameters. In order to study the range of erodibility parameters of various types of soils and the relationship between the erodibility parameters of two models and soil properties, quickly determine the erodibility parameters of the dam, a database of 279 test results were collected from the literature review as well as by contacting researchers and organizations working on erosion around the world. The samples were classified into coarse-grained and fine-grained soils according to the unified soil classification system. Correlation analysis and regression analysis of the data were used to obtain the relationship between the erodibility parameters and soil properties. Four measures were used to evaluate the statistical significance of the relationship between erodibility parameters and soil parameters for coarse-grained and fine-grained soils: R2、MSE、Fvalue/Fstatistic and cross-validation. The erodibility parameters obtained from the experimental data were compared with the erodibility parameters predicted by the regression equation, the range of erodibility parameters of different soil and correlation between erosion parameters and soil parameters were obtained. According to the erodibility parameters database, the regression equation of erodibility parameters were obtained through statistical analysis of limited soil parameters and erodibility parameters to quickly predict the erosion rate of the soil. Finally, taking Baige weir plug as an example, according to the erodibility parameter database and statistical relationship established in this study, the erodibility parameters and erosion rate were analyzed rapidly. The research findings can be used to quickly determine the erosion parameters of the dam plug body, and provide help for rapid assessment of the risk of burst flood under emergency conditions.

The Batang—Mangkang section of the G4218 highway is located in the transition zone from the Jinsha River Valley to the plateau, and facing with strong neotectonic activities, broken rock masses and frequent geological disasters. Therefore, the construction and maintenance of the highway in this region are of huge difficulties. Traditional ground geological survey methods face many difficulties in highway route selection, disaster assessment and stability analysis, etc. Combining the optical remote sensing interpretation of geological hazard points with deformation observation by InSAR technology, it is expected that the geological hazard points in this region can be investigated quickly, accurately and efficiently, and reveal their development and distribution rules of geological disaster points.Under the special geological conditions of the high mountains and valleys of the Qinghai–Tibet Plateau, the common types of geological disasters in the region were summarized, and the method of integrated highway remote sensing identification was put forward based on the study of the characteristics of regional disasters and remote sensing technology. Using this method, we carried out disaster surveys on the Batang—Mangkang section, with full knowledge of optical remote sensing visual interpretation technology and InSAR technology, supplemented by field geological survey, GIS spatial analysis, engineering geological analogy , etc. The conclusions of this article are as follows: 1) A total of 670 geological disasters were interpreted by optical visual remote sensing in the study area,and InSAR technology combined with four kinds of SAR data interpreted 220 active geological disasters; 2) The development rules of different types of geological disasters in the study area varied greatly with the change of topographic features, geological conditions and geological disasters and other influencing factors. There were differences in spatial distribution and formation lithology of geologic hazard using the optical remote sensing or InSAR technology; 3) According to the comparative analysis based on the field work, it was concluded that the interpretation results of optical remote sensing and InSAR had a certain relationship with the interpretation methods, imaging conditions of the images and the activity of landslide. The two methods cannot be used for mutual inspection directly;4) The use of comprehensive remote sensing technology was universal in the highway construction of the high mountain valley of the Qinghai–Tibet Plateau. It made full use of the complementarity of optical remote sensing interpretation technology and InSAR deformation observation technology. On the basis of saving time and cost, this method can have a more comprehensive and accurate understanding of the development of regional geological disasters.