| Currently, design of foundation pits only considering instantaneous change ofbehaviors of foundation pits, ignore effect of time on it. The large number ofengineering practice shows foundation pits has time effects, especially in the soft soilarea, its time effects behave obvious. In this paper, set foundation pit that built in thesoft soil as research object, analyze the impact generated by its creep and consolidation,based on the theoretical analysis and numerical simulation methods, the characteristicsof pit deformation under the effect of time, strut force, internal forces of supportstructure were discussed，The main content：Reviewed the development process of foundation pits, and summarizes what is thetime effect on foundation pits, summed up the current situation and the status ofresearch time effect of foundation pits of soil creep and abroad researches andconsolidation theory. Summarizes the characteristics and mechanism of deformation offoundation pits, analyze the creep characteristics of soft soil and consolidation theory,analyzing the time effect on pit’s deformation from the theoretical point combined withthe results of the two parts.Analyzing the measured values of foundation pit that built in the soft soil,found its time effects behave obvious. Based on the foundation pit that built in the softsoil, established a numerical model considering creep, analyzes the measured values of the foundation pits and comparison with the calculated values, found both of thedeformation trend and the values are coincide, and have shown time effect. Then thecalculated values of pit’s deformation, the support shaft and retaining pile’s internalforces were analyzed, the results showed that: creep of soil foundation pits wouldadversely affect the supporting structure,lead to the deformation and internal forceincreases; in addition to this most important factor of time, foundation pits depth, thephysical properties of the soil and other factors have close relationship with the timeeffect.If low level permeability clay layer including high level permeability sand layer,the impact of consolidation on the foundation pit is obvious. Based on the foundation pitthat built in this layer, established a numerical model considering consolidation, thecalculated values of pit’s deformation, the support shaft and retaining pile’s internalforces were analyzed. The results show that: compared to the supporting structure ofinternal forces, the impact of time effect on the deformation of foundation pit is obvious; consolidation is good for settlement and horizontal displacement, the impact for theheave deformation is obvious; changes in pore water pressure is the direct cause offoundation pits time effect.On the basis of theoretical and numerical analysis, discusses the measures ofcontrol deformation of foundation pits which considering creep. Pouring the floorpromptly can be well controlled total deformation of foundation pits. Select theappropriate rate can reduce the deformation of the construction pit, too fast or too slowrate are unfavorable. Intermittent construction, the exposure time of foundation pits thatwith and without support is also an important factor to deformation control offoundation pits. |
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