连续增大流量作用下泥石流冲刷起动实验研究

Experimental Study on Scouring and Initiation of Debris Flow with Continuous Increase of Waterflow

连续降水或持续融水径流冲刷土体起动形成泥石流是自然界普遍存在的泥石流现象,不同流量冲刷可诱发不同规模泥石流,然而针对持续增大水流冲刷作用下泥石流起动过程的研究较为薄弱。在对公格尔山地区冰川泥石流调查基础上,基于水槽试验,采用连续增加流量的形式冲刷冰碛土体,以近似模拟冰川泥石流的起动过程,同时监测实验过程中孔隙水压力、含水量和泥沙含量的变化,分析连续增加流量作用下冰碛土形成泥石流的起动机理。研究表明:沟道冰碛土体稳定性受内部水流渗透力和表层径流剪切力共同控制,其稳定系数与流量呈幂函数关系。不同流量冲刷下冰碛土破坏形式和起动过程不同,流量较小(<12L/min)时以渗流潜蚀破坏为主,土体并未发生明显破坏,表层细颗粒下移且渗透性增大;流量持续增大时(16L/min),土体表面出现径流且随持续水流冲刷作用下发生骨架坍塌;流量较大(>56L/min)时,土体破坏以径流冲刷破坏为主,土体表面形成冲沟拉槽现象。水流连续增大冲刷是冰碛土起动形成泥石流的关键外在控制因素,而细颗粒的大量流失降低了泥石流发生的可能性,需在更大流量下才能促使粗颗粒坍塌再次起动形成泥石流。

Debris flow initiation under presistent precipitation or continuous meltwater is ubiquitous natural phenomenon,and different waterflow scouring may induce different debris flow in scale.However,research about debris flow initiation process under the continuous increase of waterflow is weak.On the basis of investigation on glacier debris flow in Kongur Shan and artificial scouring experiment,and the scouring of moraine by continuous increase of waterflow,the initiation process of glacier debris flow is simulated.Meanwhil,by monitoring the changes of pore water pressure,water content and silt content,the author has studied the formation mechanism of glacier debris flow under continuous increase of the waterflow.Experiment results indicate that the stability of the moraine is jointly controlled by seepage force and scouring ability,and its stability coefficient and the flow rate display a power functional relation.Different waterflow possess various actual stress state,which can induce different failure mode of soil mass and initiation mechanism of debris flow.The smaller waterflow(12 L/min)is prone to with seepage damage,but the soil mass doesn’t suffer siginificant damage.With the continuous increase of waterflow(16 L/min),water flow erosion to form runoff,and then coarse particles skeleton collapse under the action of continuous erosion.When the waterflow is larger(>56 L/min),the destruction of soil is mainly caused by runoff scouring,and the surface of soil forms several gullies.Increasing the waterflow is a key external factor for debris flow initiation,and the large loss of fine particles reduces the probability of the debris flow,which can be caused by the restart of the collapsed coarse particles under larger waterflow.