###### Abstract  
A complete case record of a deep foundation pit with pile-anchor retaining structure excavated in red sandstone stratum is presented in this study. The horizontal displacement of pile top, the horizontal displacement at various depths, the axial force of anchor cable, and ground settlement during construction are measured. A three-dimensional numerical model is established to analyze the additional stress and deformation induced by the excavation and the accuracy of the FEM model is verified by comparing with field measured results. Both the measured and numerical simulation results show that the deformation of the pile-anchor supported deep excavation is significantly affected by the spatial effect. The results show that the deformation in the middle of the foundation pit is greater than the pit angle and that the deformation of the long side is greater than that of the short side and gradually decreases from the middle to the pit angle. The deformation and stress in the middle of the long side of the foundation pit are the largest, which is the most unfavorable part. With the increase of vertical excavation depth, the spatial effects tend to increase, and the influence scope of spatial effects is about five times the vertical excavation depth in the red sandstone stratum. The ground settlement outside the pit is mainly distributed in a groove shape, and the maximum settlement occurs about 8.5 m away from the pit edge. Finally, parametric studies of reinforcement parameters indicated that 1.5-2.0 times the initial elastic modulus and cohesive force of soil should be used for reinforcement. It is recommended that the ranges for pile diameter, pile spacing, anchor cable prestressing and inclination angle should be selected as 0.8-1.2 m, 1.4-2.0 m, 100-150 kN, and 10\({}^{\circ}\)-20\({}^{\circ}\), respectively. deep excavation; red sandstone; pile-anchor retaining structure; spatial effect; deformation +
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can thoroughly reflect the actual situation of deep excavations. Studies of conventional diaphragm walls combined with inner supports in sandy and soft soil areas have found that the deformation near the corners is less than that in the middle, and a large amount of data suggests that there is a spatial effect in foundation excavation [6; 7; 8; 9]. Field monitoring tests of composite structural pits in soft soil areas showed that buildings around the foundation pit were also affected by the excavation of foundation pits, with temporal and spatial effects [10; 11]. Through numerical simulating, the influence of various pit excavation and support parameters on pit deformation can be comprehensively considered, so that reasonable parameters can be selected to provide a basis for the foundation pit design [12; 13]. For deep and large excavations, support systems, such as diaphragm walls and inner supports, are relatively expensive. Soil nail wall is not optimal for controlling the deformation of foundation pits. Due to the simplicity of construction, capacity to control deformation, and low interference with pit excavation, pile-anchor support systems are frequently utilized for deep and large foundation pits [14; 15]. The pile-anchored support structure has received the attention from engineering and academic community. [PERSON] et al. [16] investigated the influence law of soil distribution and support form on the deformation of the support structure by analyzing the measurement results of several deep foundation pits. [PERSON] et al. [17] summarized the deformation form of the supporting structure in foundation pit excavation as three categories, namely cantilever type, internal convex type, and combined type. [PERSON] et al. [18] monitored the stress and displacement of the supporting pile in a pile-anchored support structure of a foundation pit, and the results showed that the bending moment of the pile gradually increased with the excavation depth, and the point of maximum bending moment gradually moved towards the bottom of the foundation pit. [PERSON] et al.