## 6 Conclusions  
Based on field monitoring data and numerical simulation analysis, this paper studies the temporal and spatial deformation characteristics of the super-deep foundation pit in the thick sandy soil area of Beijing, and, combined with the orthogonal experiment, analyzes the influence degree of different construction conditions and hydrogeological conditions on the internal structure deformation of the foundation pit and the surrounding surface settlement:  
1. Because most of the foundation pit project is located in the sandy soil, and because the compressibility of the sand itself is relatively large, under the condition of water, the rebound deformation of the foundation and the uplift of the column caused by the soil excavation are significantly larger than that under the condition of no water. The maximum deformation value of the column is between 0.54% and 0.65% He. For the construction of the super deep foundation pit, the construction method of partition excavation, digging first and then supporting, can effectively alleviate the large deformation of the internal structure of the foundation pit due to excessive unloading. 2. Due to the different embedment ratio, the displacement modes of the ground connecting wall on the north and south sides of the foundation pit are, respectively, translational mode (T) and rotation mode around the bottom (RB). The deformation generated by rotation mode around the bottom is twice that of the translational mode, and the vertical displacement Vwm of the ground connecting wall ranges from 0.3% to 0.9% He. 3. Due to the \"hysteresis\" of stress transfer in sand, the settlement deformation value first increases, then decreases, and then increases, and the settlement rate increases after the settlement deformation decreases. The surface settlement deformation in the north and south ranges from 0.2% to 2.3% He, and the influence range of excavation is four times the excavation depth. The transverse constraint and longitudinal support should be strengthened as much as possible in the design of the parapet structure, and the dispersing force can reduce the transverse deflection span ratio of the parapet structure. The embedment ratio of the retaining wall should be reduced appropriately, the displacement mode of the retaining wall should be changed, and the influence of the shear strength and saturation of the soil on the surrounding surface settlement should be considered in the design. 4. The sensitivity of six factors to the deformation of foundation pit structure and its surrounding environment is studied through orthogonal experiments. The deformationof the foundation pit structure and its surrounding environment is more sensitive to the factors of excavation unloading, precipitation amplitude, and column spacing. The main mechanism of foundation pit structure and surrounding surface deformation is soil rebound caused by excavation unloading. Increasing the spacing of columns can increase the force between piles and soils and inhibit the unloading rebound of soils. Timely and orderly dewatering can not only make the soil in the foundation pit produce the unloading compression phenomenon but also make the soil in the impervious layer produce seepage consolidation, which can effectively restrain the deformation trend of the foundation pit. 5. Based on the experimental results of 18 groups in this paper, it is concluded that the areas of strong, medium, and weak influence in the pit bottom uplift after foundation pit construction are (0-0.07) \(\times\) L, (0.07-0.14) \(\times\) L, and (0.14-0.5) \(\times\) L, respectively. In addition, when the embedment ratio is between 1.8 and 2.4, the parquet structure is in translational mode (T), and when the embedment ratio is between 2.4 and 3.4, the parquet structure is in rotation mode around the bottom (RB).