دانلود رایگان مقاله انگلیسی مطالعه بهسازی زمین در بهبود واکنش فونداسیون شمعی در خاک های گدازپذیر - اشپرینگر 2017

Abstract

In light of the disastrous the 2011 Tohoku Pacific Earthquake, the government of Japan has conducted studies to revise the seismic design code, and elevated peak ground accelerations have been adopted. Consequently, revisions on existing design to comply with the updated code are required for public projects that are still undergoing. The design safety needs to be reassessed, and implementation of strengthening measures is required if deemed necessary. For liquefaction countermeasures, ground treatment techniques that could increase the density of soils are often the preferable alternatives. The treatment usually increases the in situ SPT-N or CPT-qc values, which in turn would increase the resistance of soil against liquefaction. For many public infrastructures in Japan supported by bored piles embedded partly or entirely in sandy soils, reevaluation of design safety against soil liquefaction would be required. In an assessment of possible retrofitting countermeasures for an infrastructure foundation, ground treatment has been considered. In this case study, effect of ground treatment on response of piles in liquefiable soils was investigated with numerical analyses using FLAC. Results provide insights into this ground treatment effect and useful information for consideration in future design or decision making.

5 Conclusions

According to the study above, if simply consideration of effect of ground treatment, the suggestion to determine the range of improvement zone is that to assume the treated depth, which not more than depth of liquefiable soils, and then to decide the smallest treated width satisfied with design treated strength and vertical displacement, which not less than zero in the bottom of improvement zone. If consideration of adopting ground treatment to increase soil shear resistance in order to avoid shear failure of existing piles, the suggestion is that to determine design demands in terms of treated depth and treated strength, then to decide treated width of the improvement zone incorporating with the control of allowable lateral displacement of pile. Besides, it is need to recheck vertical displacement such that it is no less than zero. Although the effect of ground treatment in resistance of displacement is effective, but the corresponding cost is significant, most of the time the ground treatment countermeasure is not agreed by the client. Unless the other retrofitting measures are not working, the ground treatment would be limited to unformed countermeasure, and it is an inevitable problem in construction practice.