Data for the Study of Thickness for Rigid Pavement in Village Road of Expansive Soil Region

Due to the Submergence/during rainy session, CC Pavements which are constructed on the expansive soils sub grades are getting damaged due to the sub-grade soils are expansive nature. During the submerged condition/at the time of cyclones, Swell pressure develops in the sub-grade expansive soils, If this Swell pressure is more than the combined surcharge weight of Sub base and CC Pavement, uplift takes place. The swell pressure varies from 0 -2000 kN/m2 (for Bentonite) under the surcharge of 6.9 kN/m2 The surcharge weight of Granular sub base is 3.0 kN/m2 and CC Pavement is 4.80 kN/m2 resulting total surcharge weight is 7.80 kN/m2 over the sub grade. Due to confined edges of both Sub base and CC Pavement with the shoulder soils, the net uplift due to Swell pressure will be more in the middle of the pavement when compared at the edges. The rate of wetting and drying of the expansive sub grade soils always starts at edges to middle of the pavement. This leads the difference in the swell pressure more in the middle than the edges. Due to the high swell pressure at the centre of the pavement and early drying of the expansive sub grade soils at the edge of the road, longitudinal cracks will be formed almost in the middle of the road. When the expansive soil dries, due to the shrinkage in the sub grade, the pavement tries to settle down. Among both CC Pavement and Sub base, the sub-base over the sub grade will settle first leaving gaps in between CC Pavement and Sub base. At this stage, during the traffic flow, transverse cracks I crocodile cracks occurs. Also, after the formation of longitudinal cracks, the length to breadth ration of CC pavement panel will be double and influence the design of CC Pavement. The failure in the CC Pavement is due rigid and also weak in tension. Based on above observations from literature and field survey it is clear that existing design are not adequate for expansive soil hence an attempt will made to design rigid pavement for village road in expansive soil with modifications in some of existing provisions.受浸水或雨季影响，修筑于膨胀土（expansive soils）路基（sub-grade）上的水泥混凝土路面（CC Pavement）常会因路基土的膨胀特性而受损。在浸水状态或气旋侵袭期间，路基膨胀土会产生膨胀压力（swell pressure）；当该膨胀压力超过底基层（sub-base）与水泥混凝土路面的总附加荷载时，便会发生抬升现象。在6.9 kN/m²的附加荷载作用下，膨润土（Bentonite）的膨胀压力范围为0~2000 kN/m²。粒料底基层的附加荷载为3.0 kN/m²，水泥混凝土路面的附加荷载为4.80 kN/m²，因此路基上的总附加荷载为7.80 kN/m²。由于底基层与水泥混凝土路面的边缘被路肩土约束，由膨胀压力产生的净抬升量在路面中部大于边缘区域。膨胀土路基的干湿循环速率总是从路面边缘向中部发展，这会导致膨胀压力的差异呈现中部大于边缘的分布特征。由于路面中心处膨胀压力较高，且路肩边缘的膨胀土路基较早发生干燥，路面中部极易形成纵向裂缝。当膨胀土干燥时，路基会因收缩而产生沉降；在水泥混凝土路面与底基层二者中，路基上方的底基层会率先沉降，进而在水泥混凝土路面与底基层之间形成空隙。在此阶段，车辆通行时会产生横向裂缝与龟裂（crocodile cracks，俗称鳄鱼纹裂缝）。此外，纵向裂缝形成后，水泥混凝土路面板的长宽比会变为原来的两倍，进而对水泥混凝土路面的设计产生影响。水泥混凝土路面属于刚性结构且抗拉强度较低，因此易发生破坏。基于上述文献与现场调研的观测结果可知，现行设计方案并不适用于膨胀土路基；因此本研究拟对现有部分设计条款进行修正，为膨胀土地区的乡村道路设计刚性路面。