土壤持水曲線碎形維度之研究－案例説明

本文主要在於探討土壤持水曲線碎性維度之特性，其利用實驗室獲得之粒徑分佈、整體密度、粒徑密度、體積含水量及土壤水壓等資料作為模式預測之輸入參數。本文中建立三種模式，來加以推估碎性維度，並加以比較。模式一，是利用粒徑分佈資料轉換成孔隙分佈的資料藉以獲得含水量與毛細壓力，來加以推估；模式二，是直接利用實驗室實驗的獲得之土壤持水曲線中體積含水量與土壤水壓的資料並以模式來預測及推估碎性維度，模式中並分三種情況A=θ_(max)-θ_r、A=θ_(max)及A=1，加以討論，其中θ_(max)為最大飽和含水量，θ_r為殘餘含水量；模式三，與模式二相似，是利用實驗室獲得之土壤持水曲線先行使用非線性回歸以獲得方程式，在根據此方程式來分析碎性維度及A値。最後以彰化地區八個地點土樣來進行分析，求其碎性維度，並比較三種模式，結果顯示隨著模式的不同，碎性維度值亦有所差異。文中顯示模式一與模式二之＂A=θ_(max)-θ_r＂情形作為擬合條件，較合乎實驗值，所得之碎性維度值約介於1.1～1.4之間，此一結果與前人研究所得相似。

關鍵字

碎性維度；持水曲線；個案研究

並列摘要

In this study, three models were established to evaluate the characteristics of fractal dimensions for water retention curves of soils related to the particle-size distribution, bulk density, particle-size density, volumetric water content, and soil water pressure parameters which were derived from laboratory. The first model is to estimate the fractal dimension of water retention curve by using pore-size distribution data, derived from particle-size distribution, which is modeled to obtain water content and capillary pressure. The second model is to directly evaluate the fractal dimension of water retention curve by the volumetric water content and soil water pressure data which were obtained in laboratory. For the second model, there are three conditions: A=θ_(max)-θ_r, A=θ_(max) and A=1, where θ_(max) is the maximum saturated water content, θ_r is the residual water content. The third model is similar to the second model, which is using nonlinear regression analysis to estimate the fractal dimension of the soil water retention curve. Finally, these three models were applied on eight soil samples from Chung hua area. It is obvious that values of fractal dimension are model dependent. Results show that the utilization of A=θ_(max)-θ_r, as the conditions for fitting in the first and second model gave a result much closer to the experimental values. The fractal dimensions are estimated in range from 1.1 to 1.4.

並列關鍵字

Fractal dimension ； Water retention curve ； Case study

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