敦煌莫高窟顶几种典型床面蚀积量变化过程的初步观测

Process of Wind Erosion and Deposition on Typical Beds atop Mogao Grottoes,Dunhuang,China

通过对莫高窟窟顶自然和人工床面的风蚀、输导及堆积沙量变化的野外监测,初步观测结果表明:在偏西风作用下,自然状况下的戈壁床面阻截了来自鸣沙山40%的沙量,其余60%的沙量进入窟区;而偏东风又可将偏西风、偏南风作用下沉积于窟顶90%的沙量吹回到鸣沙山边缘。床面阻、输性质与沙源供给状况密切相关。沙源丰富时,风沙流以较饱和形式输送,易形成输沙床面性质;沙源匮乏时,风沙流多以不饱和形式输送,形成阻沙-输沙床面性质。砾石直径较大(>4cm)的床面主要呈现堆积性质,对偏西的风沙流阻滞功效比较明显,每100m阻沙率可达45%;偏东风作用下,每100m阻沙率可达19%;而砾石直径较小(1cm)的床面,主要以风沙输沙功能为主,是一个非堆积搬运床面。

Monitoring of wind erosion and deposition on natural and artificial beds atop the Mogao Grottoes were performed. It was founded that 40 percent sands coming from the Minsha Mountain were arrested by the natural gobi bed in condition of westerly winds, and 60 percent else sands entered Mogao Grottoes areas; On the other hand, the 90 percent of sands deposited on top of the Mogao Grottoes could be blown back to the Minsha Mountain in condition of the Easterly winds. The sand bed pattern has close relationship with sands supply and winds. When sands supply is abundant, saturated sand streams transport, so a transporting bed is easily formed, whereas, a blocking-transporting sand bed is formed when sands supply is deficient. The beds with gravel diameter more than 4 cm mainly present depositing character; their sand-arresting rate can even reach 45 percent per 100 meter in condition of the Easterly wind, and 19 percent per 100 meter in condition of the Easterly winds. The bed with gravel diameter within 1 cm mainly presents transporting character, a non-depositing bed.