数值优化方法在确定张力计反应时间上的应用性

张力计的反应时间可用于估算非饱和土的渗透系数，并可作为张力计选型的评判依据。为了更加合理且便捷地确定张力计的反应时间，先通过不同含水量条件下的泾阳黄土、定边黄土以及毛乌素砂土的土柱试验测定张力计的响应曲线，再利用半经验图解法与结合通用全局优化(UGO)算法的数值优化方法来确定反应时间，并探讨了数值优化方法的实用价值及其局限性。研究结果表明，张力计的响应曲线可分为张力计安装扰动段、压力反应滞后段以及稳定平衡段，其中，压力反应滞后段建议采用4次多项式函数拟合，而稳定平衡段则采用线性函数拟合。数值优化计算结果表明，在一般情况下，Levenberg-Marquardt优化法(LM+UGO)、BFGS准牛顿优化法(BFGS+UGO)与共轭梯度优化法(CGM+UGO)的拟合程度高，用时短，但对于数据抖动幅度较大或存在突变型曲线特征等复杂形式的张力计响应曲线，数值优化算法不易获得较理想的结果，此时仍需借由经验判断才能确定合宜的反应时间。

Use of Numerical Optimization to Determine ResponseTime of Tensiometer

The response time of a tensiometer  can be used to estimate the hydraulic properties of unsaturated soils, and it is also a critical parameter to assess the applicability  to the measurement of the transient matric suction. In order to determine the response time of tensiometer more reasonably and efficiently, Jingyang loess, Dingbian loess and Maowusu sand column tests were conducted to investigate the characteristics of time response curve of tensiometer. In addition, the numerical optimization methods based on the universal global optimization (UGO) algorithm were used to evaluate the response time of tensiometer. The results of soil colum tests show that the time response curve of tensiometer for soils can be divided  into three stages: Tensiometer installing stage, delayed response stage (pressure difference response stage), and equilibrium stage. Comparing  the results of the graphical method and the numerical optimization method, it is recommended that the delayed response stage and equilibrium stage  are fitted by a quartic function equation and a linear function equation, respectively. Moreover, the Levenberg-Marquardt optimization method with UGO algorithm (LM+UGO), BFGS quasi-Newton method with UGO algorithm (BFGS+UGO), and conjugate gradient method with UGO algorithm (CGM+UGO) are the appropriate numerical optimization methods to determine the response time of tensiometer in general conditions.