人行道构成了公路运输中的基本支撑结构。每个人行道都有多种功能要执行，必须在设计过程中进行适当考虑。根据流量要求，可以采用不同类型的人行道。人行道的设计不当会导致人行道的早期失败，影响骑行质量。

人行道类型

这pavements can be classified based on the structural performance into two,

1. Flexible pavements and
2. Rigid pavements

In flexible pavements, wheel loads are transferred by grain-to-grain contact of the aggregate through the granular structure. The flexible pavement, having less flexural strength, acts like a flexible sheet (e.g. bituminous road).

相反,在刚性路面,轮胎加载re transferred to sub-grade soil by flexural strength of the pavement and the pavement acts like a rigid plate (e.g. cement concrete roads).

除此之外，还提供了复合路面。刚性人行道上的一层柔软的路面薄层是一个理想的人行道，具有最理想的特征。但是，由于需要高成本和复杂的分析，因此很少在新建筑中使用此类路面。

1。Flexible Pavements

柔性人行道会通过grain-to-grain transfer通过颗粒结构中的接触点（请参见下面的图）。

这wheel load acting on the pavement will be distributed to a wider area, and the stress decreases with the depth. Taking advantage of these stress distribution characteristic, flexible pavements normally has many layers. Hence, the design of flexible pavement uses the concept oflayered system。A typical cross section of the flexible pavement is shown below.

Based on this, flexible pavement may be constructed in a number of layers and the top layer has to be of best quality to sustain maximum compressive stress, in addition to wear and tear.

较低的层将经历较小的压力，并且可以使用低质量的材料。柔性人行道是使用沥青材料构建的。新利客户这些可以是表面处理的形式（例如通常在低容量道路上发现的沥青表面处理），或者是沥青混凝土表面课程（通常在大容量的道路上使用，例如国家高速公路）。柔性路面层反映了下层向表面层的变形（例如，如果子等级有任何起伏，则将其转移到表面层）。在柔性路面的情况下，设计基于柔性路面的整体性能，所产生的应力应远低于每个路面层的允许应力。

灵活人行道的类型

这following types of construction have been used in flexible pavement:

• Conventional layered flexible pavement,
• 完整的 - 深度沥青路面和
• Contained rock asphalt mat (CRAM).

常规的柔性路面具有高质量昂贵材料的分层系统位于压力很高的顶部，低品质的廉价材料放在较低层中。新利客户

Full – depth asphalt pavementsare constructed by placing bituminous layers directly on the soil subgrade.

This is more suitable when there is high traffic and local materials are not available.

Contained rock asphalt matsare constructed by placing dense/open graded aggregate layers in between two asphalt layers. Modified dense graded asphalt concrete is placed above the sub-grade will significantly reduce the vertical compressive strain on soil sub-grade and protect from surface water.

柔性路面故障的原因

这major flexible pavement failures are fatigue cracking, rutting, and thermal cracking.

这fatigue cracking柔性路面是由于沥青混凝土底部的水平拉伸应变引起的。故障标准将允许的负载重复数与拉伸应变有关，并且可以在实验室确定这种关系fatigue teston asphaltic concrete specimens.

Rutting仅在沿车轮载荷路径的永久变形或车辙深度所示的柔性路面上发生。已经使用了两种设计方法来控制车辙：一种是限制子级顶部的垂直压缩应变，另一种是将车辙限制为可耐受量（通常为12 mm）。

热开裂includes both low-temperature cracking and thermal fatigue cracking.

2。Rigid Pavements

刚性的人行道具有足够的弯曲强度，可以将车轮载荷应力传输到下方更宽的区域。刚性路面的典型横截面如下所示。

Compared to flexible pavement, rigid pavements are placed either directly on the prepared sub-grade or on a single layer of granular or stabilized material. Since there is only one layer of material between the concrete and the sub-grade, this layer can be called as base or sub-base course.

In rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic plate resting on a viscous medium (see the figure below).

Rigid pavements are constructed by Portland cement concrete (PCC) and should be analyzed by板理论假设一个弹性板放在粘性基础上，而不是层理论。板理论是层理论的简化版本，它假设混凝土板是中等厚的板，它是在加载前的平面，并在加载后保持平面。由于车轮载荷和温度变化以及所得的拉伸和弯曲应力而导致的平板弯曲。

Types of Rigid Pavements

刚性人行道可以分为四种类型：

• Jointed plain concrete pavement (JPCP),
• Jointed reinforced concrete pavement (JRCP),
• 连续钢筋混凝土路面（CRCP）和
• Pre-stressed concrete pavement (PCP).

Jointed Plain Concrete Pavements是用紧密间隔的收缩接头构建的普通水泥混凝土路面。销钉杆或聚集体互锁通常用于跨接头的负载转移。他们通常的关节间距为5至10m。

连接钢筋混凝土路面: Although reinforcements do not improve the structural capacity significantly, they can drastically increase the joint spacing to 10 to 30m. Dowel bars are required for load transfer. Reinforcement help to keep the slab together even after cracks.

Continuous Reinforced Concrete Pavement: Complete elimination of joints are achieved by reinforcement.

Causes of Failure of Rigid Pavements

Traditionallyfatigue cracking被认为是刚性路面设计的主要或唯一标准。允许的负荷重复数量导致疲劳裂纹取决于弯曲拉伸应力和破裂混凝土模量之间的应力比。

最近，pumping被确定为重要的故障标准。泵送是在沉重的车轮载荷下向下移动的水泥混凝土路面的关节和水泥混凝土路面裂缝的弹出。

Other major types of distress in rigid pavements include故障，，，，spalling和恶化。

作者

Dr. Tom V Mathew(IIT Bombay)