## 1 Introduction
[PERSON] [17] measured the deformation of the soil around the passive pile under the action of lateral displacement by model tests and obtained the displacement law of the soil around the pile under different embedment depths. [PERSON] [18,19] studied the ultimate bearing capacity of anchors with different shapes and the failure mechanism of the fixed anchor length. [PERSON] [20] analyzed the horizontal displacement of the pile top, the internal force of the pile body and the single-row cantilever pile group through model tests. [PERSON] [21] conducted an in-depth study of the pile-side soil pressure and strain on the pile body of this combined structure of inclined straight piles by model tests, which also included the horizontal displacement of the outer pile. The unilateral force-deformation mechanism and damage mode of the combined structure were revealed. [PERSON] [22] studied the changes in soil stress, anchorage section stress and lateral displacement of support structure in soil foundation pit during excavation and prestressed anchor construction by large indoor model test. [PERSON] [23,24] conducted a systematic study on the deformation of the foundation pit and surrounding structures and analyzed the safety of the adjacent subway tunnel during the excavation of the foundation pit. As a non-linear elastic material, the stress, strain, and strength properties of soil under stress distortion are quite different from those under conventional perimeter pressure. Conventional model tests are conducted under 1 g (g is the acceleration of gravity), and therefore, the conventional method underestimates the earth pressure and soil deformation caused by the excavation of the foundation pit [25,26]. Centrifugal tests, which can be performed under ng conditions, can create artificial gravity to compensate for this aspect. [PERSON] [27] designed a centrifuge model test for foundation excavation used a loading system instead of excavated soil to increase the centrifugal acceleration to achieve a suitable self-weight stress state before excavation. After a series of tests, he was concluded that the real path of stress and deformation of the foundation pit could be reasonably simulated by the centrifuge model test. [PERSON] [28] studied the deformation characteristics of the foundation pit through field measurements and centrifuge model tests. It was concluded that the maximum sidewall displacements of the inner and outer pits decreased approximately linearly with the increase of the inner pit spacing but increased with the growth of the inner pit excavation width. [PERSON] [29] conducted a series of centrifuge model tests and numerical analyses. The deformation and earth pressure of the retaining structure, and the deformation characteristics of the retaining structure under various restricted soil widths, were studied. [PERSON] [30], [PERSON] [31], [PERSON] [32], [PERSON] [33], and [PERSON] [34,35] carried out a series of centrifuge model test studies on foundation pits in soft soil areas from different degree perspectives and summarized the internal force and deformation law of the support structure. Most of the above studies are focused on the economically developed soft soil areas in eastern China. Since the economic level and urban construction in the loess region of northwest China lag behind those in the soft soil region, the research on foundation pit engineering has not kept pace with the soft soil region. Foundation pit engineering has obvious regional characteristics; in other words, there is a huge difference between the engineering characteristics of loess and soft soil, which determines that foundation pits in loess region cannot copy all the experience of foundation pits in soft soil region. For this reason, it is very necessary to carry out the study of indoor model tests for foundation pits in loess areas. In this paper, based on the previous research [4,8,12,21,22], a large-scale model test study of foundation pits supported by pile-anchors was carried out using a self-researched model box.