Abstract: In view of the characteristics of pebbles in the deep foundation pit area of Zhangjiakou mountain relay center project of Beijing 2022 Winter Olympics, it is difficult to drive steel sheet piles into the supporting structure, and the use of reinforced concrete protective piles has long construction period, high cost and no environmental protection. Through scheme comparison, the support scheme of large-diameter steel pipe piles combined with small-diameter rotary jet grouting piles for water stop is finally determined, which can be recycled and reused so as to save the costs. In addition, considering the greater resistance of strongly weathered rock strata, the embedded depth of steel pipe piles is set at 1.4m, and a two-layer anchor cable system is designed. The calculation results show that the stress and deformation of the steel pipe pile meet the requirements, and the calculated horizontal displacement of the steel pipe pile is 5.16mm, which is very consistent with the measured value of 4.6mm, which indicates that the calculation of the supporting structure can reflect the actual stress state. As the rotary-jet pile is used as the stop-water curtain, there is no water at the bottom of the pit, which indicates that the water stop-water effect of the supporting structure is good during the rainy season construction. In addition, the construction monitoring scheme ensures the safety of the whole construction process and verifies the calculation results.

Key words: deep foundation pit, steel pipe pile, support design, monitoring programme

摘要： 针对北京2022年冬奥会张家口赛区山地转播中心工程深基坑区域土层中含有卵石的特点,支护结构采用钢板桩打入困难,采用钢筋混凝土防护桩工期长、造价高、不环保,通过方案比选,最终确定了大直径钢管桩结合小直径旋喷桩止水的支护方案,钢管桩可以回收再利用,节约成本。此外,考虑到强风化岩层的阻力更大,钢管桩的嵌固深度取值1.4m,设计了两层锚索体系。计算结果表明,钢管桩的受力和变形均满足要求,且钢管桩的水平位移计算值5.16mm与施工实测值4.6mm非常吻合,这表明支护结构的计算能够反映其实际的受力状态。由于采用了旋喷桩作为止水帷幕,坑底没有出现积水,表明雨季施工期间,支护结构止水效果良好,此外,制定的施工监测方案保证了施工全过程的安全,并验证了计算结果。

关键词: 深基坑, 钢管桩, 支护设计, 监测方案