细粒土路基平衡密度状态分析

为掌握细粒土路基的平衡密度状态及其变化原因，统计分析9条高速公路路床顶部的压实度和含水率检测资料，对3条黄泛区高速公路路基的压实度、含水率以及1条高速公路的路基模量进行全断面深度检测，并开展非饱和细粒土的湿化试验和弹性恢复试验。现场实测发现：在役路基除了实测含水率较最佳含水率有0~13.8%的增加外，相应的压实度出现了0~10%的线性衰减；其中，路床区、上路堤以及受水位波动影响较大的路基底部的压实度降低十分明显，而下路堤上部区域压实度基本维持不变甚至有所增大；路基压实度的变化与土的含水率密切相关。非饱和土三轴试验结果表明：土体湿化过程中，吸水导致体积膨胀和压实度衰减；当路床土吸湿至平衡湿度（含水率为18%）时，土体压实度降低5.07%。弹性恢复试验结果表明：压实路基土因变形恢复导致路基密度衰减；低含水率、高压实度和低上覆荷载条件下的弹性恢复较大，压实路床土弹性恢复导致的压实度降低值最大为0.5%；综合湿化和弹性恢复结果来看，两者占黄泛区路床区压实度衰减总量（约7%）的79.6%；此外，路基剪切模量的原位实测值较相同物理状态下的室内重塑土结果平均高出了60.64%，表明运营多年的高速公路路基土具有一定的结构性。因此，既有路基的评价应该同时考虑路基湿度增加、密度降低以及土体结构性等综合因素。

Analysis of Equilibrium Density State of Highway Subgrade with Fine Soils

To investigate the equilibrium density of the subgrade with fine soils and its development mechanism, subgrade soil compaction degrees, and moisture content were collected and analyzed from nine highways. The variations in these parameters, along the subgrade depth, were also measured at three highways in the Yellow River Alluvial Plain, along with the resilient modulus. Characteristics of the unsaturated subgrade soils were tested under hydraulic and mechanical loading. Field measurements reveal a subgrade moisture content 0~13.8% higher than their optimum level. Their compaction degrees decrease linearly by 0~10% compared to their design values. The soil compaction degree often reduces at the roadbed and the upper layer of the embankment, as well as at the bottom of the subgrade, where they are easily affected by fluctuating water levels. However, the compaction degree around the lower embankment remains unchanged or even increases. The change in the subgrade compaction degree is closely related to the soil moisture content. Results from the unsaturated triaxial tests demonstrate that water absorption during the wetting process results in the expansion of soil volume and decreases the compaction degree. When the roadbed soil reaches the equilibrium moisture content of 18%, the compaction degree decreases by 5.07%. Results from the soil resilient recovery tests indicate that the recovery of the resilient deformation of compacted soils reduces the compaction degree. Smaller initial moisture contents, higher initial compaction degree and lower overburden load cause a larger resilient recovery. The maximum reduction value of the compaction degree, caused by resilient recovery, is about 0.5% for the roadbed soil. Since the compaction degree decreases by 7%, measured in the Yellow River Alluvial Plain, about 79.6% corresponds to the soil wetting and resilient recovery. Additionally, the shear modulus of the undisturbed soils measured in the field is 60.64% higher than that of the remolded soils in the laboratory, indicating that subgrade soil might form its structure after several years of operation. Therefore, the increase in the moisture content, decrease in the compaction degree, and formation in the soil structure should be considered in the performance evaluation of the existing subgrade.