CAJ | 학술논문

排土型桩如打入桩、砂桩、石灰桩以及深层搅拌桩等的施工都会引起桩周围土体的应力变化,因此周围土体的性质也将发生变化.施工完成后,周围土体的强度将经历下降、恢复和增长的过程.深层搅拌桩施工对周围土体的作用可以归纳为以下7个方面:(1) 叶片的搅拌和固化剂的注入对周围土体的扰动作用;(2) 软粘土的触变性;(3) 施工期间周围土体的劈裂;(4) 桩身水泥浆通过劈裂裂缝向周围土体中流入及由扩散作用渗入到土的孔隙中;(5) 孔隙水中钙离子浓度增加引起的胶结作用;(6) 超静孔隙水压力消散引起的固结作用;(7) 水和作用和火山灰反应等化学作用产生的热作用.通过室内试验和理论分析来研究这些影响因素.室内试验主要研究土的触变性、土的劈裂和水泥浆扩散对软弱有明粘土的影响.理论分析则解释了土体的劈裂现象.室内试验可以直接观测到土体劈裂和水泥浆扩散现象.对于软弱有明粘土,试验结果显示周围土体的强度在70 d内由触变性得到恢复.理论分析发现即使在很小的固化剂注入压力作用下,周围土体也会发生劈裂现象.
배토형장여타입장、사장、석회장이급심층교반장등적시공도회인기장주위토체적응력변화,인차주위토체적성질야장발생변화.시공완성후,주위토체적강도장경력하강、회복화증장적과정.심층교반장시공대주위토체적작용가이귀납위이하7개방면:(1) 협편적교반화고화제적주입대주위토체적우동작용;(2) 연점토적촉변성;(3) 시공기간주위토체적벽렬;(4) 장신수니장통과벽렬렬봉향주위토체중류입급유확산작용삼입도토적공극중;(5) 공극수중개리자농도증가인기적효결작용;(6) 초정공극수압력소산인기적고결작용;(7) 수화작용화화산회반응등화학작용산생적열작용.통과실내시험화이론분석래연구저사영향인소.실내시험주요연구토적촉변성、토적벽렬화수니장확산대연약유명점토적영향.이론분석칙해석료토체적벽렬현상.실내시험가이직접관측도토체벽렬화수니장확산현상.대우연약유명점토,시험결과현시주위토체적강도재70 d내유촉변성득도회복.이론분석발현즉사재흔소적고화제주입압력작용하,주위토체야회발생벽렬현상.
Installation of displacement types of columns such as driven pile,sand compaction pile,lime compaction pile,and deep mixing column causes stress changes in the surrounding soil. The properties will change in surrounding soil.Strength of the surrounding soil will decrease,recover,and increase after column installation.The mechanisms of effects of deep mixing column installation on surrounding clay can be identified into seven categories:(1) disturbance or structure damage of soil surrounding the column due to blade mixing and expansion of admixture injection;(2) thixotropic behaviour of soft clay;(3) soil fracturing around column during mixing and expansion;(4) cement penetration and diffusion from column to surrounding soil through fractures and soil pores;(5) cementation due to increase of cation concentration in pore water;(6) consolidation effect due to increase of effective stress in surrounding soil after excess pore pressure dissipation;(7) heating caused by the chemical reaction of hydration and pozzolanic reaction. These influential factors were investigated through laboratory tests and theoretical analysis. Laboratory tests were performed to investigate the effects of soil thixotropy,soil fracturing,and cement penetration in soft Ariake clays. Theoretical analysis was employed to analyze the fracturing phenomenon. Fractures and cement penetration phenomenon were observed in laboratory test. For soft Ariake clay,test results show that strength due to thixotropic hardening regained completely within 70 days. Theoretical result shows that even in a very low admixture injection pressure, fracturing will occur in surrounding soil.