戈壁碎石土地基原状土掏挖基础抗拔试验研究

在甘肃和新疆的7个试验场地完成了40个戈壁碎石土地基原状土扩底掏挖基础抗拔试验,得到了基础抗拔荷载-位移特性。结果表明,上拔荷载作用下,戈壁碎石土地基掏挖基础具有良好的抗拔承载性能,荷载-位移曲线呈大致相同变化规律,可分为扩大端土体被压密的弹性阶段、土体剪切变形至塑性区贯通的弹塑性阶段、滑动面形成至破坏的3个特征阶段。根据基础荷载-位移曲线,采用双切线交法确定了试验基础极限上拔承载力。基于土体滑移线场理论和Mohr-Coulomb强度准则,引入抗拔土体圆弧滑动面假设,推导了戈壁掏挖扩底基础的抗拔承载力理论计算公式,并将试验结果与理论计算结果进行了对比分析。

Field Test Analysis on Belled Pier Foundations under Tensile Load in Gravel Gobi

Forty full-scale field tests were conducted on belled pier foundations at seven gravel Gobi sites in Gansu province and Xinjiang Uygur Autonomous Region in China.The uplift load-displacement response of belled pier foundations in gravel Gobi almost followed the same pattern and presented three-phase behaviors.Under tensile load,the onset of the curve usually started from the elastic linear part resulting from the compression and compaction of gravel Gobi above the enlarged base.And consequently,with the occurrence and further development of a plastic zone around the foundation,the uplift load-displacement curve turned into an elasto-plastic stage.Finally,the formation of whole rupture surface brought to the entire shearing damage of Gobi soil.The ultimate uplift bearing capacities were obtained by using the slope-tangent method for all test foundations.Based on the theory of limiting equilibrium,the Mohr-Coulomb yielding criterion and slip-line field method,the circle arc rupture surface boundary condition was introduced.And the theoretical calculation equation to determine the ultimate uplift bearing capacity of the belled pier foundation in gravel Gobi was obtained.The theoretical results were compared with those of the tests and they turned out in good agreement.