土体加固对筒型基础承载特性的影响研究

为正确评估软体地基加固对提高筒型基础承载力的影响,建立考虑土体渗流~应力耦合效应的三维数值模型,模拟了筒顶负压抽水的土体加固过程,分析了筒内土体加固对筒型基础承载特性的影响。研究结果表明:在负压加固作用2.5 d后,筒顶沉降趋于平缓,孔隙负压扩散范围广,筒内土孔隙比下降幅度大,加固效果较好。此时,筒土之间接触更为紧密,极端荷载下筒顶脱开率大幅下降。在单一加载情况下,土体加固提高竖向设计承载力42.6%,水平设计承载力129.2%,抗弯设计承载力69.6%,竖向极限承载力4.4%,水平极限承载力61.3%,以及抗弯极限承载力99.1%。在复合加载情况下,土体加固前后V~M、V~H、V~H~M包络线存在一定的差异,未加固土体筒基的包络曲线分布在加固后的筒基外侧。通过试验数据对计算模型进行验证,吻合良好。这意味着现有的筒型基础设计仍有较大的优化空间。

Study on influences from soil reinforcement on bearing characteristics of bucket foundation

So as to correctly assess the influences from the reinforcement of soft soil foundation on enhancing the bearing capacity of the bucket foundation，a 3-D numerical model that considers the soil seepage-stress coupled effect is established，and then the process of the soil reinforcement with vacuum water suction from the top cover of the bucket is simulated，while the influence from the soil reinforcement inside of the bucket on the bearing characteristics of the bucket foundation is analyzed as well. The study result shows that after 2.5 days of the reinforcement with vacuum，the settlement from the top cover of the bucket tends to be gentle and the pore negative pressure diffuses to a wider range，thus the void ratio of soil inside of the bucket is largely lowered with a better reinforcement effect. At this time，the contact between the bucket and soil becomes more and more dense and the separating rate between the bucket top cover and the soil under the ultimate loading condition is largely lowered. Under the condition of separated loading，the design bearing capacity is to be enhanced with the reinforcement by 42.6% vertically，129.2% horizontally，69.6% for bending resistance，4.4% for vertical ultimate bearing capacity，61.3% for horizontal ultimate bearing capacity and 99.1% for ultimate bending bearing capacity. Under the condition of the compound loading，certain differences are there among the envelopes of V~M、V~H、V~H~M before and after the soil reinforcement，moreover，the envelop curves of the bucket foundation with the unreinforced soil are distributed around the outside of that after reinforcement. Through the verification made on the computer model with the testing data，a better coincided result is obtained. This means that a large optimizing space is there for the design of the bucket foundation.