围岩压力是地下结构设计与施工的重要依据。新建京张城际铁路八达岭车站拟定备选方案之一的单拱超大跨设计方案中，最大的跨度近45 m。对于类似超大跨度的深埋地下结构，传统的围岩压力理论与经验计算方法都存在着明显的局限性，已经不再适用。而结合现场勘查资料和室内外试验成果的数值模拟方法，尽管可以得到相对精确的围岩压力计算结果，但存在着计算过程复杂、计算效率低下的不足。因此，在计算分析了多种传统围岩压力计算方法与数值模拟方法获得的围岩压力所存在差异的基础上，对Q系统的围岩压力公式引入跨度项进行了修正，从而获得了能够快速估算超大跨度深埋地下结构围岩压力的估算方法。最后对不同跨度工程的围岩压力进行估算，并与监测值进行比较，对比结果良好。该方法不仅可以为工程设计人员及现场工作人员提供设计计算依据，还可为相关研究人员提供理论参考。

Pressures around tunnels are the priority of the design and construction of underground excavations. One of the designs for Badaling underground station of new Beijing-Zhangjiakou intercity railway utilizes a large span single arch excavation method. In this design, the excavation span is approximate 45 m. Traditional methods to predict the rock mass pressures around tunnels are not suitable for the case in Badaling underground station because of the large span. Instead of the traditional methods, numerical simulations can provide a more accurate result but with a more complex and non computation-efficient process. Comparing the differences between various traditional calculation methods and numerical simulation method, a rapid estimation method of rock mass pressures for deep and large-span underground excavations is proposed based on the Q system. The newly proposed method introduces the factor of span into the original Q system. Comparison of surrounding rock pressures between estimated and monitoring results of underground structures with different spans shows that this method could provide engineers and designers with a quick way to predict rock mass pressures in the design and construction stage of underground excavations as well as researchers with a reference guide.