为研究隧道开挖失稳导致的地表沉陷等大变形问题，构建基于动态摩擦因数的Drucker-Prager弹塑性本构模型，并将其嵌入到光滑粒子动力学(smoothed particle hydrodynamics, SPH)数值方法的理论框架。采用筒仓颗粒流及隧道垮塌试验验证所提出的数值方法。在筒仓颗粒流试验中通过粒子图像测速技术(particle image velocimetry,PIV)观测到流动中明显的倒三角区域，并在SPH模拟中进一步得到应变场与应力场的分布，然后基于实际工程，建立隧道垮塌SPH分析模型，研究静摩擦因数和埋深比对隧道垮塌冲出距离及地表沉陷范围的影响。结果表明： 1）开挖面土方冲出距离随着静摩擦因数的减少而增大，土体之间的摩擦力降低，导致土体更容易发生滑动，使得开挖面稳定性下降； 2）随着静摩擦因数的降低，隧道开挖时土体的应力释放更加明显，导致地表沉降槽的宽度和深度增加； 3）隧道埋深比对沉降槽形状影响较大，但对于开挖面土方冲出距离影响较小； 4）随着埋深比的增大，地表沉降槽更浅且更为对称。
To investigate large deformations, such as ground settlement due to tunnel excavation instability, a Drucker-Prager elastoplastic constitutive model incorporating a dynamic friction coefficient is developed and integrated into the smoothed particle hydrodynamics (SPH) framework. The proposed theoretical framework is validated via silo flow and tunnel collapse tests. In the silo flow experiments, a distinct inverted triangular region is observed in the flow through particle image velocimetry technology. Further, the SPH simulation reveals the strain and stress field distribution. Subsequently, an SPH analysis model for tunnel collapse is established based on real engineering scenarios to examine the effects of the static friction coefficient and burial depth ratio on the runout distance of collapsed materials and the range of surface settlement. The findings are as follows: (1) The runout distance of the excavated material increases as static friction coefficient decreases, with reduced intersoil frictional resistance enhancing susceptibility to soil displacement and reducing tunnel excavation interface stability. (2) With decreasing static friction coefficient, the soil experiences a pronounced release of stresses during tunnel excavation, substantially increasing the width and depth of the surface settlement trough. (3) The tunnel cover-to-diameter ratio significantly affects the shape of the settlement trough but has minimal influence on the runout distance of excavated material. (4) With increasing tunnel cover-to-diameter ratio, the surface settlement trough becomes more developed and symmetrical.
