瞬时截面法因能快速地测定岩土材料的非饱和渗透系数,而在非饱和土的渗透特性研究中得到了广泛应用,该方法需要在渗流过程中及时测定非饱和土的含水率(吸力),但目前测量方法存在含水率(吸力)探头尺寸较大、探头与试样贴合不紧密以及测量时间较长等问题。针对上述问题,将核磁共振技术应用于非饱和土渗透特性的试验研究,对白色硅酸盐水泥试样实现快速、无损的探测,获得了试样不同截面处的含水率随时间的变化情况,并用瞬时截面法计算得到白色硅酸盐水泥的非饱和渗透系数。结果表明:白色硅酸盐水泥的非饱和渗透系数随吸力的变化很大,在4.61×10-12～7.59×10-8 m/s之间;当吸力>1 MPa时,渗透系数随吸力的降低而缓慢提升;而当吸力降至1 MPa以下时,渗透系数呈现明显的陡升,量值提高多个数量级。与传统的水分测试技术相比,核磁共振技术在非饱和土渗透试验应用中有更大的适应性。
Abstract
It is difficult to determinate the transient water content (suction) distribution in geomaterials rapidly and accurately during the permeability test of unsaturated soils. Ordinary water content measurement methods are not only time-consuming but also cumbersome with the traditional relative large probes bonded with the specimen, likely posing destructive effects on the test sample. In this paper, the water content in white Portland cement specimen was measured swiftly and non-destructively by employing the nuclear magnetic resonance (NMR) technology. The unsaturated permeability coefficients of white Portland cement were obtained by the instantaneous profile method. Results showed that the unsaturated hydraulic conductivity of white Portland cement varied greatly with suction, ranging from 4.61×10-12 to 7.59×10-8 m/s; when suction was higher than 1 MPa, hydraulic conductivity increased slowly with suction decreasing; while as suction reduced below 1 MPa, hydraulic conductivity showed a steep increase by several orders of magnitude. Compared with traditional technology, NMR technology is more applicable in measuring the water content distribution in permeability test of non-saturated soil.
关键词
非饱和土 /
核磁共振 /
非饱和渗透 /
瞬时截面法 /
含水率 /
吸力
Key words
unsaturated soil /
NMR technology /
unsaturated permeability /
instantaneous profile method /
water content /
suction
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