## 5 Conclusions  
(1) The pile-anchor support structure has good support effect for foundation pit in loess area. The reason is that the interaction of pile-soil-anchor makes the deformation of soil and support structure coordinate with each other, which can effectively restrain the lateral deformation of soil after the pile, especially as the position of the first anchor point has a more obvious limiting effect on the displacement of support pile.  
(2) Compared with cantilever piles, where the bending moment is distributed in tension on one side and compression on the other side, the pile-anchor support structure has an \"S\"-type distribution of bending moment due to the presence of prestressed anchors. With the excavation of the soil and the effect of the prestressing anchor, the maximum value of the pile bending moment and the position of the anti-bending point are decreasing. This avoids the possible extreme force state of the supporting pile, thus improving the bearing capacity of the supporting pile.  
(3) Different from the classical linear distribution of earth pressure, the active and passive earth pressure of the pile-anchor-retaining structure show nonlinear distribution due to the unloading effect caused by soil excavation on the passive side and the action of prestressed anchor. The distribution mode of the measured earth pressure is quite different from that of Rankine earth pressure, and the measured earth pressure is smaller than that of Rankine earth pressure. Therefore, the use of earth pressure theory in the design and analysis of foundation pit support should be carefully considered and verified with engineering experience, so as to ensure that the design of foundation pit support is reasonable, economic and safe.  
(4) After the prestressing force is applied to the anchors, the axial force starts to decrease at the beginning of the anchorage section and decreases to the minimum at the end of the anchorage section. The shear stress of the anchors starts to increase at the beginning of the anchorage section, reaches the peak after a certain distance, and then starts to decrease gradually.  
(5) Due to the effect of group anchors, the tensioning of adjacent anchors will reduce each other's internal force and affect the anchoring effect. It is recommended that anchor rods at the same horizontal position be tensioned at interval holes. This can reduce the prestress loss of the front anchors, and the larger the interval distance, the smaller the prestress loss and the better the corresponding anchorage effect.  
Conceptualization, Y.Z. and T.S.; methodology, T.S. and Z.W.; formal analysis, T.S., Z.W., Y.Z. and S.Y.; investigation, T.S.; data curation, T.S.; writing--original draft preparation, T.S.; writing--review and editing, Y.Z., Z.W. and S.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (Grant No. 51568042) and Technology Project of Gansu Provincial Department of Housing and Urban-Rural Development Construction (Grant No. JK2022-03).  
Not applicable.  
The data of simulation and monitoring in the article is not freely available due to legal concerns and commercial confidentiality. Nevertheless, all the concepts and procedures are explained in the presented research and parts of the research may be available upon request.  
The authors of the present work feel grateful and would like to thank National Natural Science Foundation of China, Western Center of Disaster Mitigation in Civil Engineering.  
The authors declare that they have no conflict of interest.