振动荷载及温度对白云岩和石灰岩溶蚀影响试验研究

在岩溶地区，列车运行期间的振动会对白云岩和石灰岩的水岩作用过程产生影响，再加上复杂的外界条件，这一影响会更加显著。以桂北岩溶石山地区白云岩和石灰岩为研究对象，利用自主设计的试验装置进行室内模拟试验，分别研究振动荷载及不同温度条件对白云岩和石灰岩的溶蚀的影响规律。研究发现：①常温常压条件下，在静止的酸性溶液中，白云岩的溶蚀速率小于石灰岩；②在H⁺充足的条件下，随着温度（0~45 ℃）的升高，石灰岩和白云岩的溶蚀速率都会增大，温度变化对于白云岩溶蚀影响更为显著；③白云岩和石灰岩的溶蚀受振动条件的强烈影响，二者的溶蚀量都随着振动次数的增加而增大，且在相同振动条件下石灰岩的溶蚀速率始终大于白云岩。该研究可为桂北岩溶石山地区的工程设计和建设提供理论依据。

Experimental study on the influence of vibration loads and temperatures on the dissolution of dolomite and limestone

The dissolution of surface carbonate is a complex physicochemical process constrained by multiple influencing factors. In karst regions, due to the variations in mineralogy and chemical composition of the rock mass, differences in internal structure and pore characteristics, and the influence of external conditions such as the presence of groundwater, temperatures and vibration loads, limestone and dolomite exhibit differential dissolution patterns. Such differential dissolution often damages the completeness of the rock mass, affects its mechanical property and stability, and hence poses huge risk to the safety of buildings and structures on it. With the increasing strength of China's economy and the sustained promotion of development strategies in China's western region, many tunnels and underground engineering projects are being constructed, and the speed and frequency of train operation (high-speed trains and urban rail transit) are significantly increasing. However, the repeated vibrations during train operation can alter the degree and direction of water-rock interaction, leading to the continuous expansion of joints, fractures, and cavities within the rock mass. In addition, the impact of various external factors (temperature, climate, etc.) can accelerate this process, reduce the strength of limestone and dolomite, and thus pose hidden hazards to the safety of train operation. By the self-designed experimental equipment, this study investigates the dissolution behavior of dolomite and limestone in karst mountain areas of northern Guangxi under the influence of vibration loads and different temperature conditions. The experimental setup includes vibration equipment, a constant temperature chamber, a temperature controller, a flow meter, a pH meter, equipment for measuring Ca2+ and Mg2+ ions, and related drugs and reagents. Trains traveling between urban rail transit stations undergo three phases from acceleration to uniform and then deceleration, during which the vibration amplitude changes with the speed. Assuming a train departs every 8 minutes, horizontal and vertical vibrations will be generated during the operation, with vertical vibrations being the primary cause. In the laboratory, vibration conditions were controlled using a shaker sieve machine with an amplitude of 10 mm, a frequency of 2.5 times per second, and approximately 150 impacts per minute. A crossbar was fixed to the upper part of the sieve machine, and a fine cotton thread was used to tie the rock sample to one end of the crossbar to drive the sample vibration. The vibration was conducted every half an hour for 2 to 3 minutes. The results show: (1) Under normal temperature and pressure conditions, the dissolution rate of dolomite is lower than that of limestone in static acidic solutions. (2) With sufficient H+ under different temperature conditions (0℃ to 45℃), the dissolution rates of dolomite and limestone both increases with increasing temperatures, and the effect is more significant on dolomite. At 15℃, the dissolution rate of limestone is 2.496 times that of dolomite, while at 45℃, the dissolution rate of limestone is 1.150 times that of dolomite. (3) The dissolution of dolomite and limestone is strongly affected by vibration conditions and their dissolution rates increase with the increase of vibration frequency. Under the same vibration conditions, the dissolution rate of limestone is always greater than that of dolomite. Vibration loads have a greater impact on the dissolution rates of limestone and dolomite than other factors such as temperatures. This study provides a theoretical basis for engineering design and construction in karst mountain areas of northern Guangxi.