浅谈高速公路路基料的掺拌方法

山脉与河道之间高速公路道路路基料的掺拌方法主要有堆拌法、路拌法和集中拌和法三种。这三种掺拌方法在清——伊高速公路施工的不同路段分别得到了运用,并显示了其各自的优缺点。将这三种方法进行认真的分析,对日后高速公路施工中正确的运用路基料的掺拌方法,提高工程质量有很重要的现实意义。

路基料施工技术研究

路基料作为道路的承重材料,对道路施工起到至关重要的作用。本文结合工程实例,提出采用天然砂砾石掺加适量低塑性粘土和骨料的方法,解决了天然路基料塑性指数、承载力数等不达标的问题,并通过多次反复试验研究,最终得出了最优的低塑性粘土和骨料添加比例。

便携式落锤弯沉仪在花岗岩风化料路基检测中的应用

为了确定花岗岩风化料路基模量与弯沉的快速检测方法,针对不同的花岗岩风化料路基进行了便携式落锤弯沉仪(PFWD)检测法与贝克曼梁法以及承载板法的现场试验研究。通过试验,得到了花岗岩风化料路基动静模量与动静弯沉间的关系。研究表明:PFWD测得的花岗岩风化料路基动静模量与动、静弯沉存在良好的线性关系,可用于该种材料路基弯沉及模量的快速检测和评价。

水泥和粉煤灰稳定钢渣-砼再生碎石路基混合料的制备及其性能

为减少对天然碎石的开采量,解决工业废渣和建筑固体废弃物大量堆积的问题,采用水泥和粉煤灰稳定钢渣-砼再生碎石制备路基混合料。在水泥和粉煤灰的掺量范围确定的情况下,通过干湿循环试验确定钢渣和砼再生碎石的较优质量比;当钢渣和砼再生碎石选取较优质量比时,通过三轴试验测试混合料的力学性能,进一步优化水泥和粉煤灰的质量分数;利用X射线衍射、扫描电子显微镜、能量色散X射线谱分析不同龄期制得的混合料的组成、微观结构及水化反应特征产物的变化规律,研究混合料的形成机制和强度影响因素。结果表明:当钢渣和砼再生碎石的质量比为3:1时,制得的混合料的相对强度最高,失质量分数最小;当水泥掺入质量分数为5%、粉煤灰掺入质量分数为16%、钢渣和砼再生碎石的质量比为3:1时,制得的混合料黏聚力最强,抗剪强度最大,力学性能较优;在水化早期掺入钢渣可增加钙矾石的生成量,提高制得的混合料的强度;制得的混合料的水化产物以水化硅酸钙、氢氧化钙和钙矾石为主;钙离子浓度的增加能增强制得的混合料的水化产物碱性,缩短硅酸钙水化物中的硅氧四面体链,降低制得的混合料的聚合度。

山渣料路基施工技术研究

结合西汉公路开展了山渣料路基施工技术研究。首先对试验段山渣料的路用性能进行了试验,并根据路基表面沉降量及压实度检测结果,得到采用YZ18B或YZ20E振动压路机施工时松铺厚度和碾压遍数的合理组合。随着碾压遍数的增大,山渣料中颗粒破碎率增大,且强度越低,颗粒破碎率越大。试验段填筑结束后路基顶面回弹模量普遍较正常施工路段大,各个测点测试值离散性小,满足路面要求。

高速公路废旧水稳料路基填筑施工技术研究

在城市化建设发展中产生了大量的建筑废弃物,这些废弃物对环境造成了不同程度的污染与影响。而随着各种技术手段的成熟,废旧铣刨水稳料填筑路基的利用研究逐渐深入。合理应用废旧水稳料路基可以有效地节省土方资源,提升资源利用效率,减少了对其污染以及建筑垃圾,是一种节省施工成本、提升经济效益的有效技术手段。基于此,文章主要研究了高速公路废旧水稳料路基填筑施工技术。

煤矸石路基混合料的抗压性能研究

大量堆积的煤矸石对社会和环境造成很大的影响，从变废为宝的角度出发，提出煤矸石应用到路基填筑这一观点，将有显著的社会效益和经济效益。本文对煤矸石进行室内试验分析，试验结果表明其各项技术指标均符合路基设计标准：

基于表面沉降法的铁尾矿料路基现场碾压试验分析

作为一种路基压实质量检测方法,表面沉降法具有操作简便、省时省力的优点。本文基于表面沉降法对铁尾矿料路基施工过程的碾压质量进行检测和分析,并与路基压实度进行相关性分析。研究表明,铁尾矿料路基在碾压五遍后沉降差小于2mm,达到碾压施工质量要求;松铺厚度对铁尾矿料路基碾压沉降差具有显著的影响。铁尾矿料路基沉降差与压实度呈线性负相关,当沉降差为2mm时,路基压实度达95.7%,满足规范要求。

Permanent deformation and prediction model of construction and demolition waste under repeated loading

This study aims to reveal the macroscopic permanent deformation(PD)behavior and the internal structural evolution of construction and demolition waste(CDW)under loading.Firstly,the initial matric suction of CDW was measured by the filter paper method.Secondly,the PD of CDW with different humidity and stress states was investigated by repeated load triaxial tests,and a comprehensive prediction model was established.Finally,the discrete element method was performed to analyze the internal structural evolution of CDW during deformation.These results showed that the VAN-GENUCHTEN model could describe the soil-water characteristic curve of CDW well.The PD increases with the increase of the deviator stress and the number of cyclic loading,but the opposite trend was observed when the initial matric suction and confining pressure increased.The proposed model in this study provides a satisfactory prediction of PD.The discrete element method could accurately simulate the macroscopic PD of CDW,and the shear force,interlock force and sliding content increase with the increase of deviator stress during the deformation.The research could provide useful reference for the deformation stability analysis of CDW under cyclic loading.

Mechanical properties of fiber and cement reinforced heavy metal-contaminated soils as roadbed filling

The treatment of contaminated soil is a crucial issue in geotechnical and environmental engineering.This study proposes to incorporate appropriate polypropylene fibers and cements as an effective method to treat heavy metal contaminated soil(HMCS).The objective of this paper is to investigate the effects of fiber content,fiber length,cement content,curing time,heavy metal types and concentration on the mechanical properties of soils.To this end,a series of direct shear test,unconfined compression strength(UCS)test,dry-wet cycle and freeze-thaw cycle test are performed.The results confirm that the appropriate reinforcement of polypropylene fibers and cement is an effective way to recycle HMCS as substitutable fillers in roadbed,which exhibits benefits in environment and economy development.

Effect of granite gravel content on improved granular mixtures as railway subgrade fillings

The improved granular mixtures are widely used as the fillings of railway 8ubgrade, and in order to investigate the effect of coarse grain content on granular mixtures, a series of field tests were conducted. The experimental results indicate that the permeability coefficient increases significantly with the increment of granite gravel content, especially in the range of 60%-70%. Thcrc exists a coarse grain content limit defined as 53%-58.5% to reform the permeable granular skeleton. Beyond this limit, the permeable granular skeleton is efficiently formed, and the macro pores between the separate gravels are partially filled, which is the explanation lbr the permeability increase. The investigations indicate the subgrade resistance modulus （ks0, Ev2, and Evd） depends on the granite gravel content, and the resistance modulus increases significantly beyond granite gravel content of 50%. The skeletons of granitc gravel clayey sand mixture change in the long-term deformation objected to the train-induced dynamic load, which involves three main repeated and circular deformation stages. Generally, the long-time deformation is explained as the gravel crushing and filling the internal porous space with crushed gravel fragments. Through these investigations, the C40-G60 or C30-G70 is recommended as an optimum soil mixture for the good permeability and high resistance modulus.

Stress and deformation due to embankment widening with different treatment techniques

A two-dimensional(2-D) finite element(FE) model was developed to analyze the deformation and stress of embankment on soft ground due to widening with different treatment techniques.It is found that the embankment widening induces transverse gradient change due to differential settlements and horizontal outward movements at the shoulder of the existing embankment.Embankment widening also increases the shear stress along the slope of the existing embankment,especially at the foot of slope.The failure potential due to embankment widening may increase with the increase of widening width when the widening width is smaller than 8.5 m,but may decrease with the increase of widening width as the widening width is greater than 8.5 m.The effectiveness of four ground and embankment treatment techniques,including geosynthetic reinforcement,light-weight embankment,deep mixed columns,and separating wall were compared.The results indicate that these treatments reduce the differential settlements and improve the stability.The light-weight embankment has the most effectiveness among four treatments.By using the fly-ash backfill material in widening,the transverse gradient change decreases from 0.5%-1.3% to 0.26%-0.8% and the maximum horizontal displacement decreases from 2.76 cm to 1.44 cm.

Resilient Modulus of Hydraulically Bound Road Base Materials with High Volume Waste Dust

The paper presents laboratory test results on hydraulically bound road base materials containing high volume of steel slag and blast furnace slag waste dusts compared with control mixtures. These mixtures contain higher levels of （4mm-0.0 mm） dust, than would be the case in standard un bound road base mixtures. The combined influence of the steel slag and granulated blast furnace slag wastes content is to enhance the stiffness of the road base materials and save materials and cost during road construction. Triaxial repeated load tests were performed on the unbound and lightly bound materials to measure their resilient modulus. The test results show important improvements in the bond strength between the contents of road base materials. This offers the prospect of using these materials in road base materials to reduce the use of primary aggregates and thus minimize the cost of roads and highways construction.

Characterisation, Analysis and Design of Hydrated Cement Treated Crushed Rock Base as a Road Base Material in Western Australia

Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.

Comparison of Design Thickness between the 1993 AASHTO Guide and MEPDG for Full Depth Reclamation Pavement

A research project was initiated by INDOT to estimate the structural contribution and feasibility of FDR bases for pavement structure under a low-medium volume traffic loading. FWD tests were conducted and the layer moduli were back calculated on different construction phases： the surface of existing HMA pavement, the FDR base, the new HMA final surface, and the nine months＇ traffic opening, respectively, for a total of four times. The results indicate the promise of this recycled base material in pavement construction compared to traditional granular base. In addition, this paper discusses how the lab test results relate to the expected performance in a pavement structure by the MEPDG software and its parameter effects. Research indicated the MEPDG provided comparable thickness to the 1993 AASHTO Guide if the failure criteria are set up reasonably. Therefore, the MEPDG could be used as a design tool to estimate layer thickness for FDR pavement with a low-medium traffic volume.

Comparison between responses of reinforced and unreinforced embankments due to road widening

The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional(2D) finite element(FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement,horizontal displacement,pore water pressure,and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small,it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.

甘肃金永高速公路粗粒盐渍土试验研究

为研究粗粒盐渍土作为路基填料的适用性,同时也为类似盐渍土地区公路路基的设计和施工提供数据参考,对取自甘肃省金永高速公路二标的路基料和底基层料进行室内试验研究。本试验包括筛分试验、击实试验、化学分析试验和模拟季节交替变化的大型冻融循环试验。通过室内试验,得出该地区路基料和底基层料都为砾类土,属于硫酸盐渍土;七次冻融循环后路基料土样的盐胀率为0.14%,底基层料土样的盐胀率为0.19%。

An oversize correction method of dry density for non-cohesive soils filling the embankment of high-speed railway

Non-cohesive soils have been widely used in construction of high-speed railway for their excellent physical and mechanical properties,and the determination of maximum and minimum dry density of such soils containing oversize particles is an important topic.In this study,the influence of oversize particles on dry density of non-cohesive soils is investigated by packing tests.Test results show that oversize particles will make"extra"voids around their surfaces,which increase significantly if the size ratio of oversize material to matrix material is not very big.The dry density of the total material will be overestimated by Elimination Method due to the omission of the"extra"voids.Thus,a geometric model is proposed by which the"extra"voids can be taken into account,and a new oversize correction method for non-cohesive soils is developed.Test results confirm the applicability of this method on the condition of oversize fraction being less than 40%by mass.