关键词: 竖井, 水热耦合, 冻结温度场, 数值模拟, 地下水渗流, 敏感性分析

Abstract: The authors examine the influence of groundwater seepage on the spatio-temporal evolution of the freezing temperature field during frozen shaft construction. Using field-measured data and hydrothermally coupled numerical simulations from the Yuandian No. 2 coal mine in the Linhuan mining area of the Huaibei coalfield, Anhui, China, they analyze the spatio-temporal evolution in a sand-permeated formation. Control variable method is employed to examine the effects of key parameters, including flow rate, freezing pipe spacing, freezing pipe diameter, and brine temperature, on the temperature field. Furthermore, a sensitivity analysis of the freezing temperature field is conducted using gray correlation theory to quantify the influence of each parameter. The key findings are summarized as follows: (1) During freezing shaft construction, thermal disturbances caused by excavation and wall construction significantly weaken the formation of the freezing wall along the shaft side. Groundwater seepage creates a temperature gradient of 2 ℃－4 ℃ between the upstream and downstream regions outside the freezing pipe arrangement circle. (2) Comparative analysis between numerical simulations and field-measured data confirms that incorporating soil freezing characteristic curve discrete test data into the numerical software reliably reproduces the evolution of the temperature field in the water-rich sand layer at a depth of 135 m. (3) In the water-rich sand layer, the freezing wall achieves closure after 30 days of freezing, with its effective thickness exceeding 5 m by the 100th day. Notably, the temperature field along the seepage exhibits significant heterogeneity, with pronounced differences in temperature variations between the upstream and downstream sections of the freezing wall. (4) Under singlefactor conditions, variations in freezing pipe diameter and brine temperature affect the thickness and asymmetry coefficient of the upstream freezing wall, with changes remaining under 10%. However, alterations in freezing pipe spacing significantly impact closure time, demonstrating a variation range exceeding 60%. (5) For flow rates below 5 m/d, brine temperature has the greatest influence on closure time, while freezing pipe spacing plays a key role in determining the thickness and asymmetry coefficient of the upstream freezing wall. At flow rates exceeding 5 m/d, both closure time and the asymmetry coefficient are predominantly influenced by flow rate, whereas freezing pipe spacing continues to have the largest effect on wall thickness.

Key words: shaft, hydrothermal coupling, freezing temperature field, numerical simulation, groundwater seepage, sensitivity analysis