The invention discloses a deep foundation pit open
cutting construction method, which is characterized in that vertically knocking steel plate piles are arranged on the inner side of four concrete annular beams under a foundation pit soil outlet, the upper end of the steel plate piles is positioned at the same level as the upper surface of the first concrete
annular beam, the lower end of the steel plate piles exceeds the lower surface of the lowest concrete
annular beam by a certain length, first step soil digging is started, the first concrete
annular beam is constructed, at the time, the steel plate piles are knocked in, then, the second step soil digging is started, and a soil table at a preserved soil outlet is maintained without being dug and is used for locating a digging
machine. During the construction of a section of second concrete annular beam under the soil outlet soil table, firstly, earthwork is pulled and dug under the first annular beam, the position of a section of annular beam at the soil outlet is dug, the second concrete annular beam is completed through
casting, the construction of each following concrete annular beam can be completely by parity of reasoning, and the soil is dug to the tank bottom. The method of the invention does not need to dig and fill back the earthwork platform at the soil outlet for many times, the construction program is simplified, the earthwork work load is reduced, and the construction cost is saved.