敞开式TBM施工隧道掘进段空气温度计算方法

以敞开式隧道掘进机(TBM)施工隧道为研究对象,基于热力学原理,分析掘进段热害影响因素,建立敞开式TBM掘进段空气温度的计算模型,对不同围岩级别、不同岩温下掘进段内空气温度进行计算研究。结果表明:自掘进开始,TBM掘进段内空气温度迅速升高,在掘进20min时升高至接近最大值并保持基本稳定,停机后空气温度迅速下降;掘进段空气温度随围岩温度的升高和围岩级别的提高显著上升;通风对掘进段内空气有明显的降温效果;围岩温度为18℃,Ⅱ级围岩无通风时掘进段空气温度为39.9℃,通风量为60m3·s-1时下降至27.9℃,通风控制空气温度低于28℃规范限值;围岩级别Ⅱ级,60℃岩温无通风时掘进段空气温度为81.9℃,通风量为60m3·s-1时下降至46.9℃,但空气温度仍然较高,可采用在正常施工通风基础上增加洞内局部降温措施。

Calculation Method of Air Temperature in Tunneling Section of Open-Type TBM Construction

The construction tunnel of open-type tunnel boring machine (TBM) was studied. After analyzing the factors affecting the thermal damage of excavation section, the calculation model for the air temperature in open-type TBM excavation section was established based on thermodynamic principle. The air temperatures in the excavation section of different surrounding rock grades and different rock temperatures were calculated. Results show that, the air temperature in TBM excavation section rises rapidly from the beginning of excavation. It rises to the maximum value and keeps basically stable after 20 minutes of excavation. After the TBM machine is shut down, the air temperature drops rapidly. In addition, the air temperature in excavation section increases significantly with the increase of surrounding rock temperature and surrounding rock grade. Ventilation has an obvious cooling effect on the air in excavation section. When the surrounding rock temperature is 18 ℃, the surrounding rock grade is Ⅱ and ventilation is not available , the air temperature in excavation section is 39.9 ℃. When the ventilation is 60 m 3·s^-1 , it drops to 27.9 ℃. The ventilation controlled air temperature is lower than the specification limit of 28 ℃. Moreover , when the surrounding rock grade is Ⅱ and surrounding rock temperature is 60 ℃ and ventilation is not available, the air temperature in excavation section is 81.9 ℃. When the ventilation is 60 m 3·s^-1 , it drops to 46.9 ℃, but the air temperature is still high. It is recommended to use the local cooling measures in the tunnel on the basis of normal construction ventilation.