Cast-in-place pile foundations are widely used in permafrost regions to support buildings.The stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime changes.Permafrost degradation...Cast-in-place pile foundations are widely used in permafrost regions to support buildings.The stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime changes.Permafrost degradation caused by climate change is increasing the disaster risk of castin-place pile foundations.However,proactive cooling methods for cast-in-place pile foundations are seldom reported.The cold energy produced by two-phase closed thermosyphons(TPCTs)can efficiently prevent the permafrost thermal regime from being disturbed by engineering activities and climate change.TPCTs were installed in a concrete pile forming a thermal pile.Then,a model experiment was conducted to explore the thermal regime,influence scope,dissipation process of cold energy,and freezing strength of the thermal pile.The results indicated that the thermal pile may significantly cool the foundation soil.Most of cold energy produced by the thermal pile dissipated during the warm period,and the cooling scope of the thermal pile can cover the area within a 40 cm(twice the pile diameter)radius around the pile.Additionally,the TPCTs can significantly improve freezing strength between the thermal pile and frozen soil.The lesson learned from this study can provide a new approach to control the thermal regime of cast-in-place pile foundation in permafrost,which was of valuable to the construction of pile foundations in cold regions.展开更多
Importing the interface element which links the frozen soil base with concrete piles and considering the couplings of stress field, temperature field and moisture field, this paper es- tablishes the nonlinear visco-el...Importing the interface element which links the frozen soil base with concrete piles and considering the couplings of stress field, temperature field and moisture field, this paper es- tablishes the nonlinear visco-elastic plastic finite element model of pile-soil. For a practical bridge structure the stress field and displacement field of single pile in freezing process are calculated. This paper emphatically studies the process of the tangential frost heave stress field, freezing stress field and displacement field varying with time, and ulteriorly studies time variation process of single pile carrying capacity in freezing process.展开更多
冻土与普通的土体相比具有独特的工程性质。在冻土地区进行桩基础施工后,桩和周围土体在冻土地温及大气温度的作用下逐渐回冻,回冻过程中在冰的胶结作用下桩与周围土体联结成整体共同承受外荷载作用。为了研究回冻前后桩基的承载力变化...冻土与普通的土体相比具有独特的工程性质。在冻土地区进行桩基础施工后,桩和周围土体在冻土地温及大气温度的作用下逐渐回冻,回冻过程中在冰的胶结作用下桩与周围土体联结成整体共同承受外荷载作用。为了研究回冻前后桩基的承载力变化及变形性质,在大兴安岭地区浇筑了2根15 m试验桩,试验桩中布设了温度监测系统,采集了桩基回冻过程中的温度数据。根据温度监测结果在桩基回冻前后进行了自平衡静载试验,研究了回冻前后桩基承载力、各土(岩)层的侧摩阻力及桩端阻力。研究结果表明,桩基回冻后冻土地温保持在-1.9℃桩基的承载力是回冻前承载力的1.42倍;端阻力是回冻前的1.49倍为964 k N,占桩基承载力的12.98%;各土(岩)层的侧摩阻力均有所增长,平均增长率为40.3%。研究结果可为类似冻土条件下的桩基设计及施工提供理论依据。展开更多
基金the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0905)the National Natural Science Foundation of China(42001063,41961011)+1 种基金the Open Fund of State Key Laboratory of Road Engineering Safety and Health in Cold and High-Altitude Regions(YGY2020KYPT-04)CCCC Scientific and Technological Research Program(2020-ZJKJPTJS04).
文摘Cast-in-place pile foundations are widely used in permafrost regions to support buildings.The stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime changes.Permafrost degradation caused by climate change is increasing the disaster risk of castin-place pile foundations.However,proactive cooling methods for cast-in-place pile foundations are seldom reported.The cold energy produced by two-phase closed thermosyphons(TPCTs)can efficiently prevent the permafrost thermal regime from being disturbed by engineering activities and climate change.TPCTs were installed in a concrete pile forming a thermal pile.Then,a model experiment was conducted to explore the thermal regime,influence scope,dissipation process of cold energy,and freezing strength of the thermal pile.The results indicated that the thermal pile may significantly cool the foundation soil.Most of cold energy produced by the thermal pile dissipated during the warm period,and the cooling scope of the thermal pile can cover the area within a 40 cm(twice the pile diameter)radius around the pile.Additionally,the TPCTs can significantly improve freezing strength between the thermal pile and frozen soil.The lesson learned from this study can provide a new approach to control the thermal regime of cast-in-place pile foundation in permafrost,which was of valuable to the construction of pile foundations in cold regions.
基金the National Natural Science Foundation of China(Grant No.50378043)Open Foundation of State Key Laboratory of Frozen Soil Engineering of China+1 种基金"ChunhuiProjeci of China Education Ministry"Qinglan’Talent Engineering Foundation of Lanzhou Jjactong University.
文摘Importing the interface element which links the frozen soil base with concrete piles and considering the couplings of stress field, temperature field and moisture field, this paper es- tablishes the nonlinear visco-elastic plastic finite element model of pile-soil. For a practical bridge structure the stress field and displacement field of single pile in freezing process are calculated. This paper emphatically studies the process of the tangential frost heave stress field, freezing stress field and displacement field varying with time, and ulteriorly studies time variation process of single pile carrying capacity in freezing process.
文摘冻土与普通的土体相比具有独特的工程性质。在冻土地区进行桩基础施工后,桩和周围土体在冻土地温及大气温度的作用下逐渐回冻,回冻过程中在冰的胶结作用下桩与周围土体联结成整体共同承受外荷载作用。为了研究回冻前后桩基的承载力变化及变形性质,在大兴安岭地区浇筑了2根15 m试验桩,试验桩中布设了温度监测系统,采集了桩基回冻过程中的温度数据。根据温度监测结果在桩基回冻前后进行了自平衡静载试验,研究了回冻前后桩基承载力、各土(岩)层的侧摩阻力及桩端阻力。研究结果表明,桩基回冻后冻土地温保持在-1.9℃桩基的承载力是回冻前承载力的1.42倍;端阻力是回冻前的1.49倍为964 k N,占桩基承载力的12.98%;各土(岩)层的侧摩阻力均有所增长,平均增长率为40.3%。研究结果可为类似冻土条件下的桩基设计及施工提供理论依据。
