沙漠戈壁地区水泥稳定碎石基层沥青路面拱胀调查与防治措施

Investigation of Asphalt Pavement Blow-up on Cement Stabilized Crushed Stone Base and Preventive Measures in Gobi Desert

阿拉善额济纳地区位于内蒙古自治区西北寒旱区,其境内京新高速(G7)、S312、S315路面在间隔一定距离出现了类似"天然减速带"的拱胀病害现象,严重处拱起高度达20cm,严重危及到行车安全。文章以京新高速、S312、S315为依托,调查了路面横向拱胀病害的破坏特征,并对病害段路面基层、路基不同深度(上路床、下路床、上路堤)试样的易溶盐、Cl^-、SO_4^(2-)质量分数及基层芯样无侧限抗压强度进行了分析,初步揭示了路面横向拱胀病害的产生原因。结果表明,阿拉善额济纳地区沥青路面拱胀效应随季节温度呈周期性变化,路面拱胀病害主要由水泥稳定碎石拱起所致;路面拱胀病害严重程度与路基的填挖形式有一定的关联,一般而言,填挖交界路段>一般填方路段>高填方路段>挖方路段;拱胀路段试样的易溶盐浓度大于非拱胀段,发生拱胀路段的基层、上路床、下路床、上路堤易溶盐含量明显多于未发生拱胀路段;拱胀路段试样氯离子质量分数与硫酸根离子质量分数之比小于非拱胀段,路面基层和路基含盐量越大,拱胀凸起幅度越大。拱胀路基顶面有盐分积聚现象,SEM图像发现有NaCl、Na_2SO_4侵入路面结构基层现象,受盐胀与温度疲劳应力作用,拱胀段路面基层强度明显小于非拱胀路段。路面拱胀病害是基层温度效应与基层、土基盐胀效应的耦合作用所致。结合京新高速和策达一级路成功经验,工程实践中可通过设置消胀槽、预切缝等措施减少路面拱胀病害。

The Alashan Ejina region is located in the northwestern cold and arid region of Inner Mongolia Autonomous Region.In its territory there are some defects similar to the "natural deceleration zone" occurred on the Beijing-Xinjiang Expressway(G7),S312,and S315,and the highest blow up is up to 20 cm,which severely endangers traffic safety.Based on G7 Expressway,S312,and S315,in this paper the damage characteristics of pavement blowing up are investigated,and the soluble salts at the different depths(upper,lower,and embankment)of pavement base and roadbed in the damage section,the unconfined compressive strength of the core,as well as the Cl-,SO42- mass fractions are analyzed,and the causes of the lateral blowing up of the pavement are initially revealed.The results show that the blowing up of asphalt pavement in Alashan Ejina area varies cyclically with seasonal temperature,and the arching deformation of road surface is mainly caused by arching of cement stabilized gravel.The severity of pavement arching damage and the form of subgrade filling and excavating are certain.In general,the degree of severity is cut-and-fill road section> general fill section> high fill section>excavation section.The concentration of soluble salt in the specimen of the arch expansion section is greater than that in the non-arching section.The content of easily soluble salt in the base layer,upper bed,and the lower bed of the arch expansion section on the upper embankment is obviously more than that in the unexpanded road section,and the sample of the arch expansion section is chlorine.The ratio of the ion mass fraction to the sulfate ion mass is less than that of the non-arching section.The greater the salt content of the pavement base and subgrade,the greater the arch expansion bulge amplitude.Salt accumulation on the top of the arch subgrade has been observed.The SEM image shows that NaCl and Na2SO4 penetrate into the pavement structure base and are affected by salt expansion and temperature fatigue stress.The strength of the pavement basement in the arch expansion section is significantly less than that of the non-arching road section.Pavement arching damage is caused by the coupling effect of grass-roots temperature effect and grass-roots,soil-based salt expansion effect.Combining the successful experience of the G7 Expressway and the Cedar 1st-level road,in the engineering practice,it is possible to reduce the roadway blowing up damage by providing measures such as relieving slots and pre-cutting joints.