潮湿多雨地区高速公路路基湿度的实测特征

In-situ Investigation of Subgrade Moisture of Expressway in Humid Zone

为获取潮湿多雨地区路基的湿度分布特征及其影响因素,采用现场钻芯取样和预埋湿度传感器的方法,对4条高速公路进行了现场测试.结果表明,黏土路基显著受地下水毛细作用的影响,路床内平衡含水率较最佳含水率提高5%左右,土路肩和边坡的入渗将直接影响外侧行车道以下路基湿度、提升含水率并造成一定程度的干湿循环,中央分隔带防排水措施的失效也可导致内侧行车道下含水率大幅提升;而砂土路基受地下水的影响较小,湿度波动与气候因素变化之间的滞后性也较小.因此,设计时宜充分重视防排水措施的长效性,并以受地下水位控制的路基长期湿度分布作为设计状态;若考虑到入渗产生的湿度提升与波动,以及高速公路行车道的荷载分布特征,以外侧车道的实际湿度作为设计状态则更为合适.

In order to obtain the distribution characterization and influence factors of subgrade moisture in humid zone, four expressways were investigated by coring method or time domain reflectometry （TDR） probes. The results indicate that, the groundwater table is a main factor affecting moisture distribution in clayey subgrade beneath pavement, the equilibrium gravimetric water content is about 5% higher than optimum water content; the infiltration through the uncovered shoulder and slope can increase the subgrade moisture under the outer lane, and result in the wetting and drying cycles; the poor drainability of unpaved median also leads to the water accumulation under the inner lane; thesandy subgrade is less influenced by groundwater, and the lag between rainfall and subgrade moisture variation is shorter. So, the durability of drainage facilities should be taken into consideration in highway design, and the material parameters should be selected based on equilibrium moisture content determined by underground water, especially on the actual moisture content beneath the outer lane.