极震区泥石流流量计算方法的研究

Study on discharge calculation method of debris flows in meizoseismal areas

极震区形成了大量高位能型滑坡和震裂山体,震裂山体在重力和后期降雨联合作用下,震裂面延伸、扩展和贯穿,从而形成贯通性破坏面,破坏结构,这使震裂潜在型物源转变为新崩滑体物源。极震区物源与非地震区物源迥异的物理性质,使泥石流启动的临界条件降低,导致泥石流流量在物源形成、汇流和运动过程都具有放大效应,现有的泥石流峰值流量计算方法在极震区的应用具有明显的局限性。综合考虑了地震放大效应、沟道纵坡降、沟道宽度、水动力条件和泥石流物理性质等因素对泥石流流量的影响,建立了泥石流流量-冲刷模型。对比实例验算结果和实测流量,吻合较好,说明本文计算公式对于极震区的适用性和有效性。所得成果可用以估算汶川地震中极震区泥石流流量,对泥石流防治措施的选择有参考价值。

Plenty of landslides with high potential energy and shattered mountains have been formed in meizoseismal areas. Under combined effect of gravity and rainfall,shattered surfaces start to extend and penetrate. Gradually they develop into a penetrating fracture face which breaks the internal structure of rock and soil. As a result,this process turns sources of potential shattering cracks into new landslides. The different physical properties between meizoseismal and non-seismic sources,coupled with the reduced critical condition of initiating debris flow exert an amplification effect on source formation,flow routing and movement. When applied to the meizoseismal areas,the existing methods of calculating debris flow peak discharge bear obvious limitations. This paper takes into account the fact that the discharge of debris flow is influenced by factors such as the seismic amplification effect,channel gradient and width,hydrodynamic conditions and physical properties of debris flow,and established a flow-erosion model. By comparison,the calculation result of examples by using the model is in good agreement with the actual value,which proves the applicability and validity of the formula suggested in this paper for meizoseismal areas. The results can be used for estimating discharge of debris flow in meizoseismal areas of Wenchuan earthquake and may give a reference to choosing prevention and control measures of debris flow.