棕丝改良红黏土地层基桩承载特性试验研究

Experimental Study on Bearing Characteristics of Piles in Sisal Fiber-Reinforced Red Clay Stratum

摘要: 为研究棕丝加固红黏土地基中桩基承载特性，进行了5根试桩的模型载荷试验，分析了桩基在棕丝掺量(0~0.8%)加固红黏土中的承载机理和阻力发挥特性，并采用不同方法对试桩极限承载力进行了计算，将计算值与试验值进行了比较。结果表明：随着棕丝掺量从0%逐步增加至0.8%，红黏土粘聚力先增大后减小，内摩擦角不断降低。试桩极限承载力随着棕丝掺量增加先急剧增大，在0.2%~0.6%区间内趋于稳定，后急剧降低。极限荷载条件下，棕丝掺量逐步增大，桩侧阻力占荷载比值由54.8%逐步提高至64.0%，桩端阻力占荷载比值则由45.2%逐步降低至36.0%，说明棕丝对桩侧阻力的增强效果更为显著。桩身阻力呈“R”型分布，侧阻力峰值在150~200 mm范围内。分别采用摩尔–库伦理论、邓肯–张理论和现行规范对试桩极限承载力进行计算，摩尔–库伦理论和邓肯–张理论计算值与试验值误差范围分别为−26.64%~−8.98%和−22.21%~7.68%，而现行规范计算值与试验值误差偏大。

Abstract: To investigate the bearing characteristics of piles in sisal fiber-reinforced red clay foundations, model pile load tests were conducted on five test piles. The bearing mechanism and resistance mobilization characteristics of piles in red clay with sisal fiber contents (0~0.8%) were analyzed. The ultimate bearing capacities of test piles were calculated using different methods, and the calculated values were compared with experimental results. The results indicate that as the sisal fiber content increased from 0% to 0.8%, the cohesion of red clay initially increased and then decreased, while the internal friction angle continuously declined. The ultimate bearing capacity of test piles increased sharply with rising fiber content, stabilized within the range of 0.2%~0.6%, and subsequently decreased rapidly. Under ultimate load conditions, the proportion of shaft resistance to total load increased from 54.8% to 64.0%, whereas the tip resistance decreased from 45.2% to 36.0%, demonstrating the more pronounced enhancement effect of sisal fibers on shaft resistance. The pile resistance exhibited an “R” shaped distribution, with peak shaft resistance occurring within 150~200 mm depth. Calculations based on the Mohr-Coulomb theory, Duncan-Chang model, and current design codes revealed errors between theoretical and experimental values ranging from −26.64% to −8.98% for the Mohr-Coulomb method, −22.21% to 7.68% for the Duncan-Chang model, while current code-based predictions showed larger deviations.