This project belongs to underground engineering construction technology in other technical fields. With the rapid development of urban underground space development, deep foundation pit engineering is also developing in the direction of large-scale, centralization, and differentiated shapes. For the construction of large deep foundation pits with irregular structures, the traditional forward method will generate a large amount of construction waste, dust and noise pollution; the conventional reverse method will be limited by excavation efficiency, ventilation and lighting; the large height difference in the same floor of the basement may easily lead to problems such as poor force transmission and concentrated structural stress; the development of deep foundation pits in large areas also has problems such as simultaneous construction and limited basement connection conditions. Based on this, this project innovatively proposed a new technology for top-down construction of irregular and special-shaped deep foundation pit group frames for the main structure and an underground connecting channel construction technology under restricted conditions, forming a complete set of design plans and construction techniques, and was applied to irregular structural systems for the first time. In large deep foundation pits. The main innovations are as follows: 1. The connection treatment technology for the temporary retaining row pile system of foundation pit and the inverted frame structure system is proposed. By constructing a new structural force transfer system between the retaining row piles and the frame structure, the thickness of the retaining section is optimized and the vertical structure is weakened. The connection rigidity solves the structural cracking problem caused by the differential settlement between the retaining row and the vertical structure, and at the same time ensures that the structural exterior wall and the inverted frame system are formed in one step. It avoids the problem of leakage caused by the top-down frame support system crossing the external wall of the structure. Compared with the traditional top-down method, the cost is saved by 10% and 30% compared with the normal method. 2. Developed the design and construction technology for synchronous construction of high and low spans of adjacent foundation pits. By constructing a structural transition transfer system on the adjacent edges and height difference positions of the forward and reverse foundation pits, the problem of poor force transfer caused by the large height difference between the roof of the reverse foundation pit and the ground and the problem of discontinuous force transfer caused by the large difference in the elevations of adjacent forward and reverse foundation pits. At the same time, combined with the dynamic adjustment of construction conditions, it is realized that different structural systems of adjacent foundation pits have missing layers. Simultaneous forward and reverse construction under large staggered floors saves more than 1/3 of the construction period compared with traditional group pit construction. 3. Developed deformation and internal force control technology for retaining piles under the condition of large storey high without support and treatment technology for large storey structures on the same floor. By adjusting the structural rigidity of the inverted frame, improving the soil in the pit, optimizing the earth excavation process and strengthening the horizontal constraint of the cushion layer, the deformation of retaining piles under the condition of no support at the bottom of the large-scale frame inverted foundation pit is controlled within 0.25% H. Through finite element mechanical analysis and structural design optimization of the entire frame inverted foundation pit and local fault floors, a structural conversion scheme for the same-story structure under the complex stress state of the fault floors is proposed, which ensures that the frame under the condition of limited height and width of the structural section. Main load-bearing members such as composite beams and main excavation exit edge beams transmit force smoothly at staggered floors with large height differences. 4. Propose the design and construction technology of underground connecting channels under restricted conditions between groups of pits, and develop underground connecting channels that combine hidden excavation of pipe roofs in soft soil sensitive environments with reverse construction of basement structures and penetrate the existing basement in a limited space. Road design and construction technology, realize the smooth construction of underground connecting channels under the restricted conditions where there are protected ancient trees that cannot be removed in the soil covering the channels in soft soil areas and the clear distance from the historical protected buildings is only 1m. This project applied for 10 invention patents (including 7 authorized invention patents), published 16 papers, formed 2 construction methods, edited 1 national standard, and participated in the compilation of 1 industry standard and 1 local standard. The research results have generally reached the international advanced level and have been successfully applied to deep foundation pit projects of more than 300,000 m2 in the Waigaoqiao area of Senlan, Shanghai and more than 50,000 m2 in Chuanxiao Lane and Cuiyunli in Kunming, Yunnan, with an added output value of nearly 1 billion yuan., of which the added output value in the past three years is 350 million yuan. This technical achievement has also gone abroad and is being promoted and applied to the Golden-Hill project in Vietnam, greatly enhancing the influence and competitiveness of Shanghai enterprises.