既有地下结构安全性鉴定研究

Study on the Safety Evaluation of Existing Underground Structure

上世纪70年代初哈尔滨市按照当时地铁限界标准修建了一条地下人防工程(即7381工程),隧道穿越粉质粘土、细砂土层,埋深10-20 m。为了评价7381工程现在用于地铁运营的安全性,从结构承载能力、构造、变形和裂缝等方面进行了详细检测,主要内容包括混凝土强度、混凝土碳化、混凝土表面裂缝、钢筋强度及锈蚀、隧道衬砌拱顶厚度等。在检测结果基础上,对主洞衬砌和车站三联拱的承载能力进行了计算。通过多种力学模型讨论衬砌所承受的围岩压力,并依据比较结果,推荐泰沙基模型。计算结果表明衬砌结构承载能力满足现行有关规范要求。对衬砌存在的损伤和劣化进行了机理分析,并提出了有针对性的治理方法。结合地质勘查结果和衬砌结构使用寿命评估结果得出:哈尔滨7381工程经整治后可以用于地铁运营,其剩余使用寿命估算为80年。

The project 7381 was constructed in the early 1970s, which was designed according to the subway standard at that time. This tunnel runs through silty clay and thin sand layer 10 - 20 meters beneath the ground. In order to evaluate its current serviceability for the subway, a detail investigation is conducted from the aspects of loadbearing capacity, configuration, deformation and concrete cracks. The field investigation focuses on concrete strength, concrete carbonization, concrete surface cracks, strength and rust of steel bars as well as concrete layer thickness of the tunnel arc. Based on the field investigation results, the load bearing capability of the main tunnel and the connected three arcs at station area are analyzed by finite element method. The Terzaghi Model is employed for the determination of wall rock pressure after comparison of five models. The result shows that the tunnel satisfies the relevant code in load bearing capability. The structural damage and degradation mechanism of the lining is analyzed, and corresponding countermeasures are proposed. The conclusion is that this tunnel can be used for current subway after proper renovation; the left service life is estimated as 80 years.