基于范德堡法的非饱和土电阻率测试方法

Measurement of resistivity of unsaturated soils using van der Pauw method

电阻率法是实现无干扰土体压实度及水分迁移测试的一种有效方法。范德堡法(vdP法)广泛应用于半导体等材料的电阻率测量领域,有较高的精度,将该方法引入非饱和土电阻率测试,研发了一种只接触土体表面而不破坏土体结构的土体电阻率测试装置及方法,装置由钛电极片、交流恒流源、电压采集及数据处理系统4部分组成。采用此装置对某粉黏土的电阻率进行了测试研究,验证了电极尺寸、试样高度以及温度对于测试精度的影响;测试了不同含水率、压实度下土体电阻率的变化规律,试验表明所提供的测试方法具有精度高、测试稳定、对土样无干扰等优点。

The electrical resistivity method is the main non-destructive method for measuring compaction and moisture migration of the unsaturated soils. The van der Pauw method is a well established technique for measuring the resistivity of semiconductor materials with high accuracy and suitable for a wide range of materials. The present investigation is focused on the development of an apparatus to measure the electrical resistivity and sample properties of soils based on the van der Pauw method. The proposed device consists of four parts：（1） a sensor head, which includes four Ti electrodes,（2） an AC constant current source which sends current into soils,（3） dynamic strain indicator which detects the voltage between other two electrodes, and（4） data processing system. The device is evaluated through tests on clay samples. The factors which affect the measurement accuracy, such as depth of samples, size of electrodes, temperature, are tested. By using the proposed method, the relationship among the electrical resistivity, water content and compaction of samples is investigated. The main advantages of the proposed device are high accuracy, measurement stability and no disturbance.