摘要
在Bjerrum等时e-lnσ′z曲线图的基础上,利用殷建华和Graham的一维EVP模型,在考虑土体次固结沉降的情况下,依据运行期限和运行期允许的沉降量等参数获得等载预压卸载时的临界孔隙比,进而求得控制超载预压和欠载预压卸载时的临界孔隙比,由此可计算出控制堆载预压卸载时机的临界沉降量,克服传统堆载预压依据主固结理论无法反映堆载预压降低次固结变形的缺陷。根据欠载预压的临界孔隙比公式,可计算出最小预压荷载。在推导欠载预压临界孔隙比的过程中,提出新假说A理论,证明了新假说A与假说B近似等价的充分条件。算例表明,由于考虑了软土预压期的次固结变形,堆载预压地基的总沉降量和卸载时的临界沉降量要比有效应力面积比法的大。
The critical unloading void ratio of preloading method is obtained base on Bjerrum＇s equitime e -ln σ＇z curve and Yin and Graham＇s 1-D elastic visco-plastic model. This critical unloading void ratio decided by runtime duration and allowable settlement takes account into both primary consolidation and secondary consolidation for soft clay,so farther do the critical unloading void ratios for surcharge preloading method and undersurcharge preloading method. The critical settlement for unloading time is determined by the critical unloading void ratios. It overcomes the flaws that the classical surcharge preloading method based on primary consolidation theory could not reflect mechanism where surcharge preloading reduce secondary consolidation compression deformation. The minimum preload can also be decided by the formulae of the critical void ratio for undersurcharge preloading method. In the process of deriving the critical void ratio for undersurcharge preloading method,the new modified hypothesis A is suggested The condition is proved that the modified hypothesis A is approximately equal to hypothesis B. The examples show that both the actual total settlements and the actual critical settlement at unloading time are bigger than those calculated by effective stress area method.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2010年第6期1827-1832,共6页
Rock and Soil Mechanics
关键词
堆载预压
蠕变
EVP模型
临界沉降法
surcharge preloading method
creep
EVP model
critical settlement
