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Large-scale 3D printed model test on seepage distribution in water diversion tunnel and surrounding fractured rock
Tunnelling and Underground Space Technology ( IF 6.7 ) Pub Date : 2025-01-15 , DOI: 10.1016/j.tust.2025.106389
Yajian Shao, Guowei Ma, Wei Zhang

Hydro-geomechanical model test is a prevailing method to study the seepage field in the underground engineering. Most of the existing test models are equivalent continuous medium models, whereas the deeply buried diversion tunnel in rock-matrix with fractures in practical engineering exhibit discontinuities, unevenness and heterogeneousness. To this gap, current study constructs an 1800.0 × 1800.0 × 1800.0 mm3 division tunnel model with fractures in the surrounding rock through 3D additive-subtractive printing, which registers the largest ever 3D printing hydro-geomechanical test model. The current model is based on a practical project of the Jinping II Hydropower Station. The geological strata along the longitudinal direction of the tunnel are surveyed to identify the most critical section in view of instability. Six major cracks in the critical section are identified and measured. According to the scalability principle in the fluid–solid coupling theory, the current model with dimension, density, and permeability scalability coefficients of respective 35, 1, and 35 to those of the prototype target section is designed and 3D printed. In this 3D printed model, the dip angle and direction of the six major fractures are reproduction of those of the practical fractures, while the locus spacing is reduced by a scale of 35. Structural matrix is additively printed using cement mortar, while fractures are subtractive printed with a customized cutter. The fracture space is filled with a paste medium with variable permeabilities to approach the potential permeability range in the practical fractures. To reproduce the practical hydraulic-mechanical condition in the test, the 3D model is loaded with initial stresses of 150.0 kPa and seepage condition of 20.0 kPa around the model for 7 days prior to the hydraulic loading. To cover the potential practical seepage extent, the external hydraulic pressure is set gradually at five loading levels of 40.0 kPa, 60.0 kPa, 80.0 kPa, 100.0 kPa and 120.0 kPa. The results show that, as the circulating hydraulic pressure increases, the seepage pressure inside the fracture plane and outside the lining structure gradually increases. Test results are in good agreement with the field monitoring data. There is a significant correlation between the seepage pressure in different inclination planes and the distribution characteristics of fractures in its surrounding rock. With denser fractures in the surrounding rock on the lining outside, the seepage pressure in this area will be higher. The test results reflect the discontinuity characteristics of the seepage field inside the fractured rock mass to provide guidance for the stability evaluation and long-term maintenance of water diversion tunnel engineering.

中文翻译:


引水隧洞及周边裂隙岩渗流分布的大型 3D 打印模型试验



水文地质力学模型测试是研究地下工程渗流场的常用方法。现有的试验模型大多是等效的连续介质模型,而实际工程中裂缝的岩石基质深埋导流隧道表现出不连续性、不均匀性和非均质性。针对这一差距,目前的研究通过 3D 增减打印构建了一个 1800.0 × 1800.0 × 1800.0 mm3 的分割隧道模型,该模型记录了有史以来最大的 3D 打印水文地质力学测试模型。目前的模型基于锦屏二期水电站的一个实际项目。沿隧道纵向的地质地层进行调查,以确定最关键的路段,并考虑到不稳定性。识别和测量关键部分的 6 个主要裂缝。根据流固耦合理论中的可扩展性原理,设计了当前模型,其尺寸、密度和磁导率可扩展性系数分别为 35、1 和 35,与原型目标截面的可扩展性系数相比较,并进行了 3D 打印。在这个 3D 打印模型中,六条主要裂缝的倾角和方向是实际裂缝的复制品,而轨迹间距减小了 35 倍。结构基体使用水泥砂浆增材打印,而裂缝则使用定制刀具进行减材打印。裂缝空间填充了具有可变磁导率的膏状介质,以接近实际裂缝中的潜在磁导率范围。为了在测试中重现实际的水力学条件,3D 模型加载了 150.0 kPa 的初始应力和 20 的渗流条件。在液压加载前 7 天,模型周围为 0 kPa。为了覆盖潜在的实际渗流范围,外部液压逐渐设置为 40.0 kPa、60.0 kPa、80.0 kPa、100.0 kPa 和 120.0 kPa 五个负载水平。结果表明:随着循环水压的增加,裂缝面内部和衬砌结构外的渗流压力逐渐增大;测试结果与现场监测数据吻合较好。不同倾角面的渗流压力与其围岩裂缝分布特征存在显著相关性。随着外衬周围岩石的裂缝较密集,该区域的渗流压力会更高。试验结果反映了裂隙岩体内部渗流场的不连续性特征,为引水隧洞工程的稳定性评价和长期养护提供指导。
更新日期:2025-01-15
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