Advanced Materials Research Vols. 594-597

Abstract: The importance of protection and utilization of the topsoil as the soil seed bank in road construction and vegetation recovery has not attracted enough attention. Through analysis of topsoil protection and utilization as well as current situation of road vegetation recovery, it is proposed that using the local topsoil resources which containing richful seed bank for road vegetation recovery is very effective. And it is the technical reference for the road vegetation recovery.

Abstract: Based on the typical Pavement-Subgrade structure form of western expressways, the interaction of the Pavement-subgrade system under vehicle load is researched. The model of stress transmission is established through numerical simulation. The vehicle load transfers stress to subgrade surface via the pavement structure layers. According to the different properties and functions of pavement layers, similar pavement layers are combined into equivalent structure layers. In this study, stress distribution of vehicle load on subgrade surface is analyzed according to the different degrees of thickness and stiffness of the equivalent structure layers. Also, the effect of different subgrade fillers on stress transmission is studied.

Abstract: Mechanics properties of lime- fly ash stabilized soil are investigated. First, the chemical composition of fly ash are analyzed by spectral analysis test. Compaction experiments of all mix proportion projects are carried out in different water conditions to obtain the optimum water contents. Then the optimum mix proportion is obtained by the unconfined compressive strength and the compression rebound modulus test. Finally, the pavement structures design for a highway of lime- fly ash stabilized soil road sub-base is done. By the comparison, a conclusion can be drawn that lime-fly ash stabilized soil is suitable for flexible pavement or semi-rigid pavement because of its good strength and rigidity which can effectively reduce thickness of the lower pavement and basic deflection.

Abstract: We propose a comprehensive and multi-functional Overpass Pedestrian System to alleviate the serious traffic congestions in metropolitan areas of big cities in China. It is composed with three major parts: switching and connecting part, transportation part and service facility part. Compared with the pedestrian system and foot-bridges in some busy intersections in urban areas, this system is more efficient and human-oriented on separating pedestrian and vehicles. It can not only relieve the traffic congestion but also increase the comfortable level of walking. Differs from average isolated and single-functional foot-bridges, the system provides pedestrians with more pleasant walking experiences, thus increases pedestrians’ willing to use this system.

Abstract: In view of the shortage of using operating speed to evaluate the safety of highway alignment, we bring forward the use of possible speed. After establishing the computing models of axial, transverse and vertical acceleration, we obtain the methods and steps of predicting possible speed; with that, we describe the standards, methods and steps of highway alignment evaluation using possible speed.To the sections of highway whose alignment parameters are beyond the valuation standards, the solutions are respectively put forward which are amending the alignment parameters or setting the security facilities. Finally, a section of a secondary highway along a river is used as an example.

Abstract: Highway safety is one of the targets of the road design, coordination of highway design index and the actual vehicle speed is the key. According to the analysis of automobile speed observation data, established the plain or hilly area two road car model, put forward highway alignment design safety evaluation standards and safety design method.

Abstract: with the development of our country highway traffic to large flow, large axle load and channelized traffic direction, traffic volume and the changes of axial load composition to the present asphalt pavement structure, causing the pavement service capacity declines, structure damage occurs early, rut problem is one of the main factors of asphalt pavement quality, so the anti-rutting in the asphalt mixtures were studied in this paper.

Abstract: Choose appropriate preventive maintenance measures is the key link to the pavement preventive maintenance successfully and effectively. According to the characteristics of highway asphalt pavement preventive maintenance technology, it summarizes the applicable and inapplicable occasions and application note of existing preventive maintenance measures, puts forward the preventive maintenance technology characteristics and adaptability, sets up the frame of decision-making for the preventive maintenance measures to provide guarantee for successful implementation of effective preventive maintenance.

Abstract: In order to study the applicability and strengthening effect of impact compaction technology in wetness and softness loess roadbed treatment, impact compaction technology was applied in ground treatment and layered filling roadbed compact of a freeway sub-grade construction, and compactness and settlement of the soil were also measured. Test results suggest: impact compaction technology can effectively apply to shallow wetness and softness loess roadbed treatment and the most effective depth is about 80cm, and this effect appears to increase with the impact compaction times and 30 impact compaction times is the most suitable. As regards the layered filling sub-grade, when the loose paving thickness is 40cm, compactness after 40 times compaction can satisfy specified demand. At the same time, combined with the test settlement, the control criterion of impact compaction quality is investigated.

Abstract: Temperature change of the semi-rigid base course is one of the reasons of the appearance of the reflective crack. The stress intensity factor of the semi-rigid asphalt pavement is calculated with the finite element method. Sensibility analysis is made on the parameters (modulus, thermal expansion coefficient, thickness) affecting the magnitude of the stress intensity factor. Above all, it is concluded that the graded gravel can reduce the reflective cracking