文章以通过下穿繁忙道路下的2个矩形大断面超浅埋暗挖工程为例，介绍采用锁扣管棚预加固、全断面注浆、型钢拱架支护、分大断面为小断面错位开挖等一系列超浅埋暗挖法设计与施工技术。表明在城市不宜明挖的条件下，采用超浅埋暗挖矩形大断面地下通道有较大的技术优势，并提出： 1）采用锁扣管棚是本工程成功的关键，设计时应充分考虑各种工况，设计计算可采用弹性支点法，在入口1H（H为洞高）范围内，管棚内力及支反力变化较大，应仔细考虑，而其后为一般开挖段，内力及支反力均趋于稳定； 2）施工前对地下管线进行详细探查尤为重要； 3）长距离锁扣管棚施工难度较大，钻进工艺由原来钢管全程双线约束，改为一线一点约束，管棚施工可以顺利进行。

The paper innovates the design and construction method of ultrashallow buried excavation by introducing an example of two ultrashallow buried excavation rectangular tunnels, including prereinforcement with lock pipe roof, fullface grouting, steel arch support and excavation of both big and small crosssection, etc. The example proves the advantages of ultrashallow buried excavation when open excavation is impossible in cities and offers the following suggestions: (1) As the use of lock pipe roof is the key to success, multioperation conditions should be considered in design, and flexibility fulcrum method should be used in design calculation. In the entrance 1H range, pipe roof internal force and support reaction changes greatly, to which special attention should be paid. Afterwards it is in a normal excavation stage, pipe roof internal force and support reaction tend to be stable. (2) It is particularly important to explore the underground pipeline in detail before construction. (3) As the construction of long lock pipe roof is difficult, the drilling technology has changed from steel pipe double line restraint to one line one point constraint to make pipe roof construction smooth and feasible.