Cement Pile Composite Soil Nailing System By Force And Deformation Analysis

Soil nailing technology has been used widely at home and abroad since its first use in 1970s, but its work mechanism hasn't been explored entirely until the present time. In these days, the two main calculation models for soil nailing are soil-nailed-wall and soil-slope anchorage and stabilization.Composite retaining of cement-soil pile and soiling nailing (CRCSPSN) has been used for solving the problems in soft soil, such as water-sealing, seepage-stability, pre-retaining, etc. CRCSPSN is a kind of retaining form, which combines cement-soil pile and soiling nailing, so its mechanism is more confusion than soil nailing. There is no consensus design method up to the present, and design theory is far behind engineering practice.CRCSPSN shows lots of difference from soil nailing in deformations and carrying loads, because the functions of cement-soil pile. By comparing with soil nailing, the functions of cement-soil pile in CRCSPSN are entirely analyzed for the first time in this paper. At the same time, reasons for reducing side displacement of pit, accelerating excavation speed, rationalizing internal forces in soil nails, refining surroundings are also found out.The mechanism of CRCSPSN is analyzed and researched a lot in Tongji University, and a conclusion has been put forward, which is that CRCSPSN system and the soil retained form into an artificial side-slope. The double functions of soil nails, anchorage and consolidation, are not changed in CRCSPSN. In this paper, based on the mechanism above and the engineering practice in Zhengzhou, the incremental regularities of deformations and carrying loads are analyzed, and the design models, which reflect the construction characters in CRCSPSN, are put forward.In this paper, the main ideas include that,(1) based on the theory of soil-slope anchorage and stabilization, the incremental calculation method for soil nail forces in soil nailing is put forward;(2) the functions of cement-soil pile in CRCSPSN are entirely analyzed for the first time, and taking the functions of cement-soil pile in maintaining the stabilization of foundation-pit into consideration, the incremental calculation method for soil nail forces in CRCSPSN is brought forward, and based on the work mechanism above and failure modes of CRCSPSN, the design mode of CRCSPSN is presented;(3) after the design of soil nails in CRCSPSN, the deformation calculation model and the simplified model that are based on the deformation coordination between soil nails and cement-soil piles, are established for the first time;(4) for verification the theory of incremental calculation performing under the mechanism of soil-slope anchorage and stabilization in soil nailing and the simplified calculation model for side-displacement of CRCSPSN, some engineering cases are calculated, and the results are compared with measured values, what have been done show that the theories established in this paper are all correct and effective.