| Continuous Arched Soil-cement Retaining Structure (CASRS), which has been putted into application just since a few years ago, is one of the supporting types for deep foundation pits. The buttress of CASRS is composed of soil cement mixing piles, which are arranged into the form of arch, and the springs are consisted of borehole cast-in-place piles. Compared with ordinary line bracing structures, the CASRS has more technical advantages in force resisting, deformation controlling, economy saving, time limiting, and underground space saving. Practical engineering shows that its deformation is smaller than common line supporting systems, and the compress-high property of cement material is fully utilized because the buttress is mainly under compressive stress.Till now, CASRS has been studied by many researchers, and a number of designing and calculating methods about it have been introduced. However, there are two similar defects in all of these researches. Firstly, the value and distribution of earth pressure that acted on the back of the retaining structure are assumed befor analyzing, and the interaction between earth pressure and the deformation of supporting structure is ignored. Secondly, all of the earth pressure is assumed to have been transfered to spring piles through arch body, while the situation is not considered that the arched retaining structure will transfer the load to its lower part when bearing bending loads. Finally, a number of simplifications and presuppositions have been taken into the analysis of the structure, thus the result can not reflect the reality.Based on summarizations of formal researches, the CASRS is analyzed under its spatial force state and is numerical simulated with the aid of three dimensional finite element methods. The major work is listed as follows.(1) The spatial force state of the arched retaining structure is analyzed in order to study its working mechanism, and the existence of load distribution in horizontal and vertical directions under the effects of earth pressure in CASRS is validated.(2) The notion of horizontal arch body and vertical arch body is putted forward for the first time, and based on the coordinate deformation in springs of vertical arch body with of horizontal arch body, the distribution law of earth pressure on the two directions is deduced. The notion of earth pressure bearing coefficient of horizontal arch body at the excavation depth is proposed on the basis of the worst-case internal force principle. After that, with the aid of stress intensity theory, a new calculation model for CASRS is given in this paper.(3) The numerical simulation method is employed to analyze the structure after theoretical study, and the three dimensional model of CASRS is built for researching with using FEM software. The simulation is carried out while considering both the interaction between soil and bracing structure and the three dimensional boundary of CASRS. Referring to the results, the items, such as the level displacement of the supporting structure, pit settlement and swell, earth pressure distribution along both horizontal and vertical direction, the spatial stress state of the cement-soil arch, and the loads acted on spring piles, are studied, and furthermore, the distribution ratio of earth pressure on the horizontal and vertical directions is worked out.(4) A systematic behavior analysis of CASRS is carried out to study the influence of the variation of parameters of bracing structure to the retaining effects. The factors, such as arch height, arch span, arch buttress thick, the dimension of spring piles, the depth of cement-soil arch, the length of spring piles, are taken into account to analyze the retaining effect. Through the analysis, the reasonable values for these parameters are pointed out which can be applied as a theoretical guide for engineering practice. |
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