Experimental study of the freeze-thaw resistance of MICP-treated soil
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摘要: 近年来微生物诱导碳酸钙沉积技术(MICP)受到学界的广泛关注,在土体加固领域也取得一定进展。微生物加固后土体性能整体得到提升,但是冬冻春融的循环作用,使得土体结构逐渐松散,导致土体强度、抗冲刷性和保水能力均有所降低。目前针对冻融循环对MICP固化土性能影响研究较少。本文采用喷洒法对试样表面进行MICP固化处理,对多组试样给与不同冻融周期作用,并进行无侧限抗压强度测试、冲刷试验和水分蒸发试验,探讨试样水分蒸发速率随冻融周期增加的变化规律,以及冻融对加固土性能的影响。基于土体抵抗冲刷破坏作用机理,结合不同冻融周期下试样的表观松散程度和试验结果,探究冻融循环导致加固土性能下降的原因。试验结果表明:试样无侧限抗压强度(UCS值)从43.83kPa提高到加固后的69.92kPa,经历20次冻融循环,加固试样的UCS值为未加固试样1.48倍,且加固试样冲刷侵蚀量远小于未加固试样的一半。研究表明微生物诱导生成的碳酸钙沉积物能够有效填充土体内部孔隙,粘结松散土颗粒,从而大幅提高土体强度,有效削弱冻融对土体的破坏作用。虽然冻融循环作用周期增加使得土体的加固效果逐渐劣化,但在短期冻融环境下,MICP加固后土体仍具有较高的强度,并能有效抵抗雨水的冲刷侵蚀作用。
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关键词:
- 微生物诱导碳酸钙沉积 /
- 微生物加固土 /
- 冻融循环 /
- 雨水冲刷
Abstract: [Objective] Microbially induced carbonate precipitation (MICP) method is a potentially effective and environmentally friendly technique to improve the unfavorable soil conditions. MICP treatment can improve soil strength. However, the durability of MICP-treated soil under freeze-thaw cycles has not been investigated. [Methods] This study investigates the effects of freeze-thaw cycles on unconfined compressive strength, erosion resistance, and water retention capacity of soil which treated with MICP under different conditions. The surface of the specimens was treated using the spray method, and then some specimens were subjected to erosion tests. Unconfined compressive strength (UCS) and water evaporation rate of the specimens under different freeze-thaw cycles were tested. Combining the mechanism of soil resistance to erosion damage and the test results of specimens under freeze-thaw cycles, the reasons for the deterioration of reinforced soil properties due to freeze-thaw cycles are investigated. [Results] The results show that the UCS of the sample has increased from 43.83kPa to 69.92kPa after MICP-treated. After 20 freeze-thaw cycles, the UCS of the MICP-treated sample is 1.48 times that of the uncured sample, and the erosion amount of the MICP-treated sample is much less than half of that of the uncured sample. The results indicate that the microbially induced calcium carbonate deposits can effectively fill the internal pores of the soil and bind the loose soil particles, thus significantly improving the soil strength and effectively weakening the damaging effect of freeze-thaw on the soil. [Conclusion] Although the consolidation effect of the soil gradually deteriorated due to the increase of the freeze-thaw cycle, the MICP-treated soil still had high strength under the short-term freeze-thaw environment and could effectively resist the erosion effect of rainwater.
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