上海粉砂土在人工冻结条件下的导电特性试验研究

在初始含水率和密度与原位土一致的情况下,通过电阻率试验对上海地铁四号线的粉砂土进行了在30～-30℃条件下的导电特性试验研究。结果表明:未冻水含量较高时,粉砂土的导电性在高电压情况下随着电压的升高而增强;在含水率和密度一定的情况下,粉砂土的导电性与温度密切相关,即电阻率随温度降低而增大,也就是说其导电性随温度的降低而减弱;在温度高于0℃条件下,粉砂土的电阻率随温度变化相对较小;在温度低于0℃条件下,粉砂土的电阻率随温度变化较明显;在30℃≥t≥0℃,0℃t≥-10℃及-10℃t≥-30℃三个温度段,分别拟合出温度与电阻率之间相关度较高的回归方程。上述结论可为今后长江三角洲地区类似土层采用电阻率法监测冻结壁的发育状况提供物理基础。

Experimental study on electrical conducting characteristics of silty soil in Shanghai under artificial freezing

Under the initial water content and the density of the test soil are the same to that of the undisturbed soil,the electrical conducting characteristics of silty soil for Line 4 of Shanghai Metro are studied by using resistivity method under 30 ～-30℃.The results indicated that： when the unfrozen water content is relatively high,the electrical conducting characteristics of the silty soil would change with the voltage increase under high voltage;when the water content and the density are in definite values,there is the close relationship between electrical conducting characteristics of silty soil and the temperatures,namely the resistivity of the soil would increase while its temperature falls;when the temperature is above 0℃,the range of the resistivity variation of the soil is relatively low when the temperature changes;when the temperature is below 0℃,the resistivity of the soil would obviously change when the temperature changes;under the three temperature sections with 30℃ ≥t≥0℃,0℃ t≥-10℃ and-10℃ t≥-30℃,three regression equations with high correlation degree are fitted respectively.The above conclusions could provide the physical basis for monitoring the development of the freezing walls in similar soil layers by resistivity method in the Yangtze River Delta.