京张高铁八达岭长城站耐久性设计方法及措施

为了提高隧道及地下工程的耐久性,降低地下工程运营期维修养护的成本,采用系统分析法研究地下工程的耐久性机理,提出地下工程结构耐久性的计算模型及其定量化设计方法。隧道结构的耐久性取决于初期支护和二衬承载力的衰减,初期支护承载力的衰减将引起二衬荷载的增大,隧道结构耐久性的安全系数可采用二衬承载力与其荷载的比例来表示,当二衬荷载增长曲线与其承载力衰减曲线相交时,隧道结构达到承载力极限状态,此时也即为隧道耐久性的设计使用年限。八达岭长城站支护体系设计中,采用围岩长期自承载的设计理念,利用长寿命初期支护加固围岩,形成持久的围岩自承载拱,长期承担全部围岩荷载,二衬作为安全储备。同时,增加锚杆注浆保护层的厚度和密实度、设置居中定位器来提高锚杆的耐久性,采用分段高压注浆来提高锚索的耐久性,采用中低热水泥、Ⅰ级粉煤灰、多级配整形骨料、控制入模温度、优化配合比、进行保湿保温养护等措施提高二衬混凝土的耐久性,形成长寿命支护结构体系。

Design Method and Measures of the Durability of the Great Wall Station on the Beijing-Zhangjiakou High-speed Railway

In order to improve the durability of tunnel and underground engineering and reduce the cost of maintenance and maintenance during the operation period, the durability mechanism of underground engineering is studied by using system analysis method, and the calculation model and quantitative design method of durability of underground engineering structure are put forward. The durability of tunnel structure depends on the attenuation of initial support and second lining bearing capacity, and the attenuation of initial support bearing capacity will lead to the increase of second lining load. The safety factor of tunnel structure durability can be expressed by the ratio of second lining bearing capacity to its load. When the load growth curve of the second lining intersects the attenuation curve of the bearing capacity, the tunnel structure reaches the ultimate state of bearing capacity, which is also regarded as the design service life of the durability of the tunnel. In the design of the support system of the Badaling Great Wall Station, the long-term self-bearing design concept of the surrounding rock is adopted, and the surrounding rock is reinforced by the initial support of the long service life to form long-term surrounding rock self-supporting arch and undertake permanently the full surrounding rock load, and the secondary lining is reserved for safety. Meanwhile, the thickness and compactness of the anchor rod grouting protective layer are increased, and a centering positioner is arranged to improve the durability of the anchor rod. Subsection high pressure grouting is adopted to improve the durability of the anchor cable. Some measures, such as medium and low heat cement, grade I fly ash, multi-grade plastic aggregate, controlling injection temperature, optimizing mix ratio, moisturizing and heat preservation maintenance are employed to improve the durability of the secondary lining concrete.