地下工程涌水涌砂诱发的沉降试验研究

针对地下工程中涌水、涌砂诱发的沉降问题，设计了一套可以改变涌口直径模拟水、砂涌出的可视化试验装置，对不同厚跨比及砂土中不同细颗粒含量下涌水、涌砂诱发的沉降规律进行了研究。试验结果表明：当厚跨比大于某一数值时，砂土中无论细颗粒含量多大，土体均不会发生沉降；当厚跨比在一定范围内、细颗粒含量小于某一数值时，土体会发生沉降，大于该数值后，土体会发生溃砂；溃砂发生的临界细颗粒含量与厚跨比初期呈抛物线上升关系，后期保持水平；当厚跨比小于某一数值时，砂土中无论细颗粒含量多小，均会发生溃砂；圆形涌口涌水、涌砂诱发的沉降在平面上呈圆形，剖面上近似二次曲面；土体溃砂后的沉降范围与沉降曲面的形状破坏角有关，沉降曲面的形状破坏角大致比土体天然休止角大9o。

Experimental study of settlement caused by water and sand inrush in underground engineering

To understand the mechanism of the settlement caused by water and sand inrush in underground engineering, a set of visual test device that can change the blow mouth diameter and simulate gushing of water and sand is designed. This device can vary the condition of different thickness-to-span ratios and different contents of fine particles in sandy soil. When the thickness-to-span ratio is more than a certain value, regardless how much content of fine particles in sand, the soil will not settle. When the thickness-to-span ratio is within a certain range and the fine particles is less than a certain value (i.e. critical fine particle content), the soil will settle; if the fine particle content is greater than the critical particle content, sand burst will occur in the soil. The critical fine particle content of quicksand increases parabolically with the thickness-span ratio at the initial stage, but remains at a level at the later stage. When the thickness-to-span ratio is less than a certain value, regardless how much content of fine particles in sand, quicksand will occur. The settlement induced by water gushing and sand gushing in circular mouths is circular in plane and quadric in profile. The settlement scope after quicksand is related to the shape damage angle of subsidence surface, which is roughly 9° larger than the natural angle of repose of the soil.