###### Abstract  
This paper focuses on investigating the stability of a deep foundation pit with hard surrounding rocks at different excavation stages with different supporting schemes by means of numerical calculations. The supporting schemes in question were combinations of one fixed vertical support and four varied transverse supports. Drilled grouping piles were used as vertical supports, and the commonly used steel bracings and prestressed anchorages served as transverse supports. The parameters used to evaluate the stability of the foundation pit at different excavation stages included the lateral displacements of the surrounding rocks, the settlement of the surrounding ground, the axial forces of steel bracings, and displacements at the tops of the drilled grouting piles. Simulation results showed that when a transverse supporting scheme consisting of one-layer steel bracings and prestressed anchorages set at 9 m and 22.5 m underground, respectively, was adopted, the lateral displacements of the surrounding rocks and settlement of the surrounding ground at different excavation stages were the largest compared to those under the other three transverse supporting schemes, while the corresponding values were lower compared to those allowed in Chinese standard GB50007-2011, demonstrating that this kind of supporting scheme is effective in terms of ensuring the safety of the foundation pit at different excavation stages. Moreover, the setting techniques for this kind of supporting scheme were relatively simple, and the corresponding influences of supporting element arrangements on excavation techniques were the lowest. Therefore, one-layer steel bracings and one-layer prestressed anchorages constituted the most suitable transverse supporting scheme for excavating a deep foundation pit with hard surrounding rocks. stability; deep foundation pit; hard surrounding rocks; transverse supporting; deformations 2024 Usually, the surrounding rocks of a foundation pit in downtown areas are soft soils or soft rocks, and it is more challenging for engineers and researchers to come up with a suitable supporting scheme to ensure the safety of foundation pits, especially deep foundation pits, because during excavation, excessive displacement of the surrounding soft soils or soft rocks may occur, threatening the stability of these deep foundation pits [8; 9]. Usually, the supporting structures for excavating a deep foundation pit in soft soils or rocks include a retaining structure to restrain the displacement of the surrounding soils and inner supporting structures to control deformations of the retaining structure and the surrounding ground. However, it is not easy to determine supporting schemes for a deep foundation pit, since costs, manpower, construction sequences, and techniques, as well as the safety grade of deep foundation pits as specified in the Chinese standard of Code for Design of Building Foundations (GB50007-2011) [10], should also be taken into consideration [11]. During the past few decades, investigations at home and abroad have always concentrated on safety evaluations for deep foundation pits with soft surrounding rocks [12; 13]. [PERSON] et al. [14] adopted a support scheme consisting of bored piles and prestressed anchor cable supports combined with concrete corner bracings to ensure the safety of an ultra-deep foundation pit in soft soils influenced by groundwater. [PERSON] et al. [15] adopted a combined support system consisting of prestressed composite pile-anchors and miniature steel pipe piles to guarantee the safety and stability of a deep foundation pit in fill soil areas. [PERSON] et al. [16] adopted a support scheme consisting of a suspended diaphragm wall with two rows of struts set in the upper part and five prestressed tiebacks set in the lower part. [PERSON] et al. [17] adopted a support scheme consisting of underground diaphragm walls with four inner supports composed of concrete bracings and pre-stressed steel bracings.