预置管法静力触探检测水泥搅拌桩损伤控制方法研究

Damage control methods for detecting cement mixing piles by static cone penetration tests in reserved tubes

预置管法静力触探实施水泥搅拌桩完整检测时存在桩体损伤问题。基于模型桩实验和数值模拟方法研究预置管法静力触探检测水泥搅拌桩损伤控制方法。模型桩实验表明,插管直径影响探头的贯入轨迹,插管强度影响检测结果的灵敏度;数值模拟显示,静力触探贯入插管损伤桩体的程度与插管直径、管壁厚度、桩体强度有关,与贯入深度、插管强度无关;静力触探贯入引起的桩体等效塑性应变与插管的直径大小、管壁厚度负相关;引起的损伤区范围与桩体龄期和插管直径负相关,最大半径随插管直径增大近似为双曲线趋势衰减。现场检测时,在试桩阶段依据数值模拟预先确定插管尺寸的有效范围,由现场试验选择确定工程检测用插管的尺寸,达到控制检测损伤桩体完整性的目标。

The problem of pile damage encountered when using cone penetration test(CPT) in a reserved tube for quality detection testing is addressed. Based on the experimental and numerical models, the damage control methods for CPT in reserved tubes are studied. The results of CPT show that the penetrating path of probe and the sensitivity of detection are influenced by the diameter and strength of the tube. The numerical results show that the damage degree of the pile depends on the diameter and thickness of the tube and strength of the pile, as opposed to the depth of cone penetration and strength of the tube. The equivalent plastic strain of the pile is negatively correlated to the diameter and thickness of the tube. The area of damaged zone is negatively correlated to the age of mixing pile and diameter of the tube. The maximum radius of the damaged area decreases with the increase of the tube diameter. In the field tests, the effective range of the sizes of tubes is determined in advance according to the numerical simulation, and the size of the tubes used in engineering tests are determined by the field tests, so as to achieve the goal of controlling the integrity of the damaged piles.