隧道下穿既有线爆破方案的研究与实践

某隧洞下穿鹰厦线工程，工程地质水文地质复杂，下穿段铁路路基为半路堤半路堑形式，路堤边坡坡度约为i：0．75，且铁路右侧为九龙江，铁路轨底到隧洞顶的覆土厚度约为20m。爆破方案的设计与实施十分复杂，在详述工程概况、工程地质和水文地质条件的基础上，从爆破方案的选择、爆破参数的确定以及爆破技术的实施等多个方面对隧道下穿既有鹰厦线方案进行了详细的论证和阐述，研究的结论和实践经验对同类工程有较好的借鉴作用。

The Study and Practice of the Blasting Scheme for a Tunnel Under-Crossing the Existing Railway

With a certain tunnel under-passing the Ying-Xia Railway, where both the engineering geological and hydrological conditions are very complex, the roadbed of the under-passing railway is of the half-embankment and half-cut form, with the fall- ing gradient of the side slope of the embankment being 1：0.75, the Jiulong River right located on the right side of the railway and the depth of the covered layer of earth between the bottom of the railway track and the top of the tunnel being about 20 me- tres. In this case,the design and implementation of the blasting scheme is extremely complex. Upon the basis of introducing the outline, the engineering geological conditions and the hydrological conditions of the project in detail, the construction scheme of the tunnel under-passing the existing Ying-Xia Railway is testified and dealt with in detail from the angles of the choice of the rational blasting scheme, the determination of the blasting parameters, the implementation of the blasting techniques, etc. The conclusion of our research and our practical experience may serve as a useful reference for other projects of the same type.