大型天然黄土洞穴系统现场冲刷试验

摘  要：通过现场冲刷试验，结合勘探、调查及室内含泥率测定等手段对大型天然黄土洞穴系统的三维空间展布特征、水文特性及侵蚀特征进行了研究。结果表明：黄土洞穴系统侵蚀过程具有明显的期次性；洞穴过水流量过程曲线可分为增加阶段、相对稳定阶段和减小阶段三个特征流量段，其中在第一阶段普遍存在“滞流效应”，第二阶段具有小幅波动的特性，并发现洞穴内的总渗流损失量随设计注水流量的增大而有所增加；根据含泥率随时间变化曲线，分析了不同流量过程段含泥率的变化特点，通过不同工况的累积侵蚀量对比发现洞穴的侵蚀速率与流量显著正相关。从机理上对产生上述过程、现象及结果的原因进行了合理解释，为黄土潜蚀机理及潜蚀速率的研究提供了可靠的现场试验数据。

FIELD WATER FLUSHING TESTS ON LARGE-SCALE NATURAL PIPE-CAVE NETWORK IN LOESS

This paper presents the results of the field water flushing tests into sinkhole,  exploration, investigation and laboratory sediment percentage tests in loess. It aims to examine the three dimensional distribution, hydrographic characteristics and erosion characteristics of the large-scale natural  pipe-cave network in loess.   The findings are summarized as follows. At first, the erosion process of the natural pipe-cave system in loess was periodical. Secondly, each of the water flow curves in the pipe-cave system includes three different characteristic stages:   (a) the amount of water flow kept  increasing, (b) the amount of water flow became constant, and (c) the amount of water flow became reducing.  During (a), the "retardance effect" of water flow  always happened. During (b), the amount of water flow had a limited fluctuation And the seepage quantity increased  as the injected water increased. Thirdly, the changes of sediment percentage during the three  stages were analyzed from the sediment percentage-time curves. The erosion velocity shows a positive correlation with the flow quantity from the accumulative comparison of erosion quantity in the designed cases. Finally, the causes of all the processes, phenomena and results mentioned above are explained. The data obtained from this work provide a valuable base for the research on both the mechanism and the velocity of sub-erosion in loess.