## 2 Overview of the Project and Layout of Measurement Points  
### Overview of the Project and Layout of Measurement Points  
The pit project is located in the downtown area of Shanghai, adjacent to the metro station on the east and residential buildings on the remaining three sides. The pit area is about 7800 square meters, divided into two areas: Area I is the area of the underground joint construction section, which has been completed, and Area II has an area of 5720 square meters, with a three-level basement and an excavation depth of 15.4-15.9 m. The enclosure structure is a 1 m-thick diaphragm wall, with triaxial hydraulic soil-mixing piles on both sides of the wall to reinforce the channel wall, and three reinforced concrete supports in the vertical direction, but a fourth steel angle support is set up in the northeastern corner of the local area. The periphery of the pit is reinforced with triaxial soil-mixing piles for skirt reinforcement, the width of reinforcement is 8 m, and the depth of reinforcement is 6.0-7.0 m below the bottom of the pit. Among the buildings around the pit, the nearest place on the north side is a five-storey shallow foundation brick-concrete structure residential building, which is about 9 m away from the enclosing edge line; on the west side, it is close to two six-storey shallow foundation brick-concrete structure residential buildings, which is about 9 m away from the enclosing edge line; on the east side, it is close to the underground station, and the distance is about 34.17 m; the nearest place on the south side is a six-storey residential building with a shallow foundation of a brick-concrete structure, which is about 13 m away from the edge line of the enclosure; the surrounding buildings are represented by F, G, H, I, and J. Buildings F and G are concrete buildings, and buildings H, I, and J are brick-concrete buildings. The plan layout of settlement monitoring points for deep foundation pit construction buildings is shown in Figure 1, where F1 is the first monitoring point of building F, and other monitoring point symbols' definitions are by analogy (for example, G2 is the second monitoring point of building G). The main basis for monitoring is the 'Foundation Pit Engineering Construction Monitoring Regulations' (DG/TJ08-2001-2016) [23]. For monitoring, the settlement monitoring points are set up using the L-type peg arrangement method on the buildings arranged within the range of 2 \(H\) (\(H\) is the depth of the pit excavation) around the foundation pit construction area, and at least 3 points of elevation data are set up outside the range of 3 \(H\) around the foundation pit, and the co-ordinates of the control points are obtained through the establishment of a levelling measurement monitoring network. The elevation of each monitoring point is measured by the line work point, and the initial value is measured before construction, the difference between the current elevation and the previous elevation is taken as the current settlement, and the difference between the current elevation and the initial elevation is taken as the cumulative settlement. In this study, the monitoring of surface settlement and building settlement was carried out using an electronic level, and the accuracy of the monitoring data was in percentile in millimeters. The monitoring alarm value is as follows: the maximum settlement rate reaches 2.0 mm/d, or the cumulative settlement reaches 20 mm. The soil layers within the excavation depth of the pit are the \(\copyright\)1 layer, \(\copyright\)1 layer, \(\copyright\)1 layer, and \(\copyright\)1 layer, and the soil at the bottom of the pit is mainly the \(\copyright\)4 or \(\copyright\)1 layer. According to the investigation report and ref.