土钉抗拔试验对粘结强度估计的影响

传统的土钉设计方法经常低估了土钉的粘结强度，从而导致了不经济的设计。为此，在土钉抗拔试验结果的基础上，提出了采用贝叶斯理论来估计粘结强度的新方法。建立了粘结强度的先验分布，讨论了未破坏试验、部分破坏试验和破坏试验3种情况下粘结强度的更新。结果表明，抗拔试验能够有效地提高粘结强度估计的精度。无论抗拔试验是否做至土钉破坏，更新的粘结强度变异系数都小于先验的变异系数。当抗拔试验都未做至土钉破坏时，更新的粘结强度均值大于先验的均值；当抗拔试验都做至土钉破坏时，更新的粘结强度均值小于相应的先验值。随着最大试验荷载的增加，更新的粘结强度均值逐渐增大，但更新的变异系数逐渐减小。

Impact of Soil Nail Pullout Tests on Estimation of Bond Stress

The conventional design approach of soil nails often results in an underestimation of bond stress, which in turn gives an uneconomical design. Therefore this paper aims to propose a methodology to account for the effect of pullout tests on the bond stress. This procedure is formalized in the Bayesian framework. The prior distribution of bond stress is formulated on the basis of the available pullout test data. Three cases of Bayesian updating of bond stress based on pullout tests are studied; namely, all pullout tests not conducted to failure, a part of pullout tests conducted to failure, and all pullout tests conducted to failure. The results indicate that the updated coefficient of variation of bond stress can be significantly smaller than that before the pullout tests. The updated mean bond stress is higher than the prior value when all pullout tests do not conduct to failure. The updated mean bond stress is smaller than the prior value when all pullout tests conduct to failure. With the increase of test loads, the updated mean bond stress increases, but the updated coefficient of variation decreases.