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Taking dolomite and limestone in Guilin and Liuzhou regions in the north of Guangxi Province as research objects, this paper analyzed their mineral composition and chemical composition, and then carried out the chemical corrosion test, the corrosion test under the chemical-temperature actions, and the corrosion test under the action of vibration load, respectively. The results showed that: (i) the dolomite in northern Guangxi mainly has fine crystalline texture and massive structure with low content of acid insoluble matters, while limestone mainly has powder crystalline texture and massive structure with high content of acid insoluble matters, and the purity of both dolomite and limestone are very high; (ii) the difference of corrosion between dolomite and limestone mainly depends on the ratio of CaO/MgO in their chemical composition, and the content of silica and acid insoluble matters; (iii) the corrosion rates of the pure dolomite and the pure limestone are basically the same under the same external conditions; (iv) temperature and vibration load have relatively large influence on the corrosion rates of dolomite and limestone, and the corrosion rates of dolomite and limestone increase with the increase of temperature, but the influence of vibration load on the corrosion rate is more significant than temperature. This research can provide theoretical basis and technical support for large-scale engineering construction and prevention of karst geologic disasters in karst stone mountainous areas in the northern Guangxi. Keywords: dolomite and limestone; structural features; corrosion characteristics; northern Guangxi

The phenomenon of rocky desertification is obvious in karst plateau of Guizhou, China, and the distribution area of slight–medium–severe rocky desertification is very large in Zhenfeng–Guanling–Huajiang, Guizhou. To explore the cause of formation and development of rocky desertification in the region, the karst development mechanism and characteristics were studied by the method of indoor dissolution test and microscopic analysis. The results show that the dissolution and karst features of carbonate rocks are closely related to geological structure, hydrogeological conditions, and lithology. The dissolution rate is the most affected by the chemical composition and mineral composition, followed by the pore structure and the particle feature. The dissolution rate of carbonate is in positive proportion with the calcite content, while it decreases with increasing content of dolomite. In the same chemical composition, the rock with the finer grains has a faster surface dissolution rate. In addition, the erosion amount will change with the pore aperture and connectivity. Karst morphology is mainly affected by the microstructure and mineral assemblage characteristics of carbonate rocks. In this rocky desertification area, bare rock over a large area will be further eroded, which will form the stone bud, stone forest. At the same time, the hydrodynamic effect of groundwater will erode the rock deeply, and the depression, karst funnel, or deep valley will appear gradually.

The Guang-Qing freeway reconstruction and extension project is located in Guangdong province, China, extending from Guangzhou city to Qingyuan city. The total project length is 57.6 km, 33 km of which is in a karst area where sinkhole collapses are common. Therefore, there were concerns about the safety and security of the roadbed, bridge piles, and other structures associated with the original roadway. The study addresses karst development, covering layer (overburden), and external factors that contribute to catastrophic sinkhole collapse along the project. The study found that the formation of sinkhole collapses is affected significantly by the degree of karst development and soil characteristics, including thickness. Collapses may be triggered directly by external factors that disturb the natural equilibrium. Such factors include heavy rainfall that impacts soil and groundwater conditions, as well as vibration and groundwater flow disruptions that are caused by pile construction and other engineering activities. Prevention measures were adapted to local conditions and optimized based upon safety, reliability and cost-effectiveness.