EXPERIMENTAL INVESTIGATION ON MOVEMENT AND STRESS FLUCTUATION OF QUICKSAND INSIDE FISSURE

In recent years, coal mining gradually has transformed from eastern region to western region of China and the quicksand disaster had received increasing attention. This paper presents a series of experiments on the influencing factors of quicksand and the stress inside fissures caused by quicksand. Two different man-made quartz sand and other three natural sand samples are used in two quicksand test equipment set ups designed by authors. The experiment with two man-made quartz sand shows that the speed of quicksand mainly depends on the width of outlet. The total amount of quicksand mainly depends on the sand resource. Controlled by the fissure dip angle, the opening pattern of the quicksand passage can be divided in three types: the local space expanding, the local space moving and quicksand directly. The experiment with three natural sand samples show that stress decreases along the entrance to the outlet of fissure model regardless of dry sand or sand and water mixture flow. According to the stress variation, the transportation of water and sand mixture can be classified into two type: the collision transporting type, such as sand sample 1,which observed stress fluctuation; the continuous transporting type, such as sand sample 2 and sample 3,the stress changes continuously. All the dry quicksand of three natural sand samples can cause stress fluctuations to the fissure. The stress, the amplitude and period of fluctuation are larger when quicksand formed by larger particle. The stress fluctuation frequency of dry quicksand are about 3.2~3.6Hz by interpolation analysis with Matlab. For sand and water mixture flow, the stress fluctuations are only monitored in sand sample 1. When the frequency reduced to 2.7~3.5Hz and controlled by the particle size, the stress raises with little range. The outcomes can contribute to understanding the movement mechanism of quicksand and the stress dynamic inside fissure. It also has an important guiding to avoiding and preventing quicksand disaster.