旱涝急转下斜墙坝渗流特性试验研究

Seepage behaviors of inclined wall dams under drought-flood abrupt alternation

对斜墙坝渗流安全,关注点多在于是否形成稳定渗流场,浸润线高低以及渗流量多少等,渗流分析基本为饱和渗流,而在旱涝急转情况下,受旱土体处于非饱和状态,土体表面分布着裂缝,渗流情况复杂,常规渗流分析难以进行。基于室内坝坡模型,模拟旱涝急转工况,研究斜墙坝渗流特性。研究结果表明：对于受旱后裂缝发育程度低的黏土防渗体防渗性能良好,其渗透系数要小于饱和渗透系数,而对于裂缝较发育区域,由于其良好的透水性,渗透性远大于土体饱和时的渗透性;降雨及水位上涨时,裂缝会自行愈合,但愈合仅限于表面,土体完整性无法再回到产生裂缝前的状态,此时坝坡土压力值相对试验初期要小许多,裂缝的产生增大了土体的孔隙率,改变了土体渗透性,永久削弱了黏土防渗体防渗性能。试验得出了旱涝急转下斜墙坝渗流演变规律,可据此对实际工程中的渗流薄弱部位进行重点监测与保护。

Most seepage safety analyses for dams focus on the evaluation of stable seepage field, infiltration line and seepage flow. However, under drought-flood abrupt alternation, the soil surface becomes cracked, making it too complicated to conduct a routine seepage analysis. The seepage characteristics of an inclined wall dam under the drought-flood abrupt alternation are studied using a large-scale physical model. The results show that after drought, the permeability coefficient of clay with low crack development is smaller than the saturated permeability, but for the cracked areas with high permeability, the permeability coefficients are much larger than the saturated permeability. As the water level rises, the cracks can heal themselves, but this healing is superficial, and the soil can no longer return to its pre-drought state. After crack healing, the integrity of the dam slope is much less than that of its original state. In addition, the formation of cracks increases the porosity of the soil and changes its permeability, which permanently weakens the anti-seepage performance of the clay soil. The seepage flow behaviors of the inclined wall dam under fluctuating drought-flood conditions are evaluated, and the results can be used to monitor and protect the weak parts of seepage dams in practical projects.