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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70d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。
Dumping piles, such as driven piles, sand piles, lime piles and deep mixing piles, will cause the stress changes of the soil around the piles, so the properties of surrounding soil will also change. After the construction is completed, the strength of the surrounding soil will experience a process of decline, recovery and growth. The effect of deep mixing pile construction on the surrounding soil can be summarized as the following seven aspects: (1) the stirring effect of the blade and the infiltration of the curing agent on the surrounding soil; (2) the thixotropy of soft clay; (3) construction (4) The pile grout flows into the surrounding soil through the cleavage cracks and infiltrates into the pores of the soil by diffusion; (5) The cementation caused by the increase of the calcium ion concentration in the pore water; (6) Consolidation caused by dissipation of excess pore water pressure; and (7) Thermal effects of chemical interactions such as water and ash reactions. Through laboratory experiments and theoretical analysis to study these factors. Laboratory tests focused on the thixotropy of soil, the influence of soil cleavage and the diffusion of cement slurry on the weak and clear clay. Theoretical analysis explains the cleavage of soil. Indoor test can be directly observed in the soil split and grout diffusion phenomenon. For weakly clayey clays, the test results show that the strength of the surrounding soil is restored by thixotropy within 70 days. Theoretical analysis shows that even with a small injection pressure of curing agent, the surrounding soil will also split.