Comparative Study of Pile Pillared Support and Pile-anchor Retaining in Deep Pit Chengxiang Wang, Chengkun Lu, Wei Han, Hongsong Sun and Huailiang Kou E3S Web Conf., 143 (2020) 01042 Published online: 24 January 2020 DOI: 10.1051/e3sconf/202014301042