Roads In Regions Research Articles

Low-cost road construction and rehabilitation in unstable mountain areas

Rationale When designing the construction or rehabilitation of roads in unstable mountain regions subjected to floods, landslides, erosion and earthworks failures, it has become usual practice to employ a selection of the techniques described in Section 2. The need for adequate land surface evaluation in this context is obvious: (i) the information so produced is essential to many if not most design processes; and (ii) proper evaluation of topography, materials and geohazard is central to the performance of the road construction, and its maintenance in the longer term. These concepts are embodied in Fookes et al. (1985) and in Overseas Road Note 16 (Transport Research Laboratory 1997) which deals specifically with geohazards and road design in unstable mountain areas. The selection of the techniques, and the manner in which they are applied, will depend on project area conditions, the availability of the necessary data or documents, and the nature of the engineering scheme being proposed. The techniques are usually applied in a progressive manner, with the need to refine and detail ground conditions more closely as the site selection and design procedure takes place. The conclusion to this process is the usual inevitability that final design will not be established until ground conditions are fully defined during construction. In the case of road rehabilitation projects, existing cut slope exposures provide a more or less continuous record of soil and rock conditions above the road, while the stability of slopes and the observed distress to the existing road pavement provides a useful overview of stability, and the reaction of slopes and drainage channels to road works in general. These benefits obviously do not accrue in the case of new road construction. The design case studies for a proposed new road in Nepal and the rehabilitation of an existing road in the Philippines are described below to illustrate the value of land surface evaluation techniques in each case.

ROAD GRANTS, INTERGOVERNMENTAL COMPETITION AND THE BENEFITS OF DUPLICATION

Abstract: This article argues that direct commonwealth involvement in road funding and road policy has benefited the states and local government. Although inefficiencies and friction are evident as a result of joint funding, the benefits of multiple accountability outweigh the costs. A competitive dynamic underlies the involvement of all three levels of government, producing outcomes that no single government dominates, but which reflect in part the responses of each to their respective constituencies. The commonwealth has been driven to more intrusive forms of intervention as existing controls failed to achieve the commonwealth's objectives, and to expanding its financial contributions to counter the diversion of funds by state governments. Its commitment to funding the road program is likely to be highest when its specific purpose grants can be identified closely with the provision of roads in particular regions and localities. In sum, joint funding of the road program produces a system that is responsive to competing conceptions and interests, and the commonwealth's “voluntary vacancy” from all but “national” roads is on balance likely to be detrimental to the program.

Thermal Model For Roads, Airstrips And Building Foundations In Permafrost Regions

Abstract A thermal model describing the one-dimensional heat conduction in a layered system is developed. Up to ten homogeneous layers, each having different thermal properties porosity, water content and thickness, can be accommodated. A periodic temperature is input for the surface condition. The computed results consist of the depth of the thawed region as a function of time. The layered model is applied to the design of foundations for roads and airstrips in permafrost regions. A sensitivity study was made to find the effect on thaw depth of varying physical properties of the materials used, the geometry of the construction and the surface temperature. The means for extension of the model to building foundation design by modification of the surface boundary condition is presented. Introduction THE DISCOVERY OF OIL in the Prudhoe Bay region of Alaska has focused considerable attention on the engineering problems of developing petroleum production facilities in remote arctic areas. The main source of difficulty is the undesirable thawing of permafrost under such structures as roads) airstrips, buildings and drilling equipment. Subsidence, differential settlement and frost heaving may be expected if the permafrost formation under the structure is allowed to thaw seasonally or permanently(1). In order to guard against such destruction, building sites may be placed on gravel embankments which; in turn, may rest on a thermal insulator as is common in road construction on the arctic tundra(2). In order to insure adequate and economical protection of the underlying permafrost, accurate predictions of the temperature distribution and the depth of thaw under engineering structures become important. It is the purpose of this paper to present a thermal model for calculating the seasonal depth of thaw in a layered medium; it is applicable to general structures where the heat flow is essentially one-dimensional. In this model heat transfer is assumed to be due exclusively to conduction. For pure ice-water mixtures (such as ice on lakes) this assumption is inadequate because of convective effects(3). It is recognized that on a microscopic scale the exact mode of heat transfer in permafrost is likely to be a combination of conductive, convective and radiative processes(4); however, on the basis of soil temperature measurements, Pearce and Gold(5) were able to conclude that "the annual temperature variation in the soil ... is remarkably consistent with the theory of (conductive) heat flow in a one-dimensional semiinfinite medium." Thus, a conduction model may be used with confidence for temperature studies in permafrost. This problem has been investigated by Lachenbruch(6) for a system limited to three layers. Our model and discussion to some extent are parallel to that of Kazemi and Perkins(7). The basic difference, apart from the structures studied, is in the solution algorithm used for solving the heat flow equations. The method proposed here is mathematically sound(8), easy to apply, allows a fine spatial resolution and is quite fast. In fact, the discussion of construction methods for roads and airstrips is based on a parameter study conducted via interactive computer graphics.

Role of sintering in snow construction

BECAUSE of the almost complete lack of roads in the polar regions, the ability to land aircraft on snow has always been of great importance in polar operations. In Greenland the first operation that utilized aircraft landings on snow was that of Ellsworth and Amundsen with Riiser-Larsen and Dietrichson as pilots in 1925. The following year Byrd flew his ski-equipped Fokker trimotor to the North Pole with Floyd Bennett as pilot. In 1928-29 the skiplane was introduced to the Antarctic by Byrd [1]. Since then landing on skis in Greenland and the Antarctic has gradually become a routine matter. Since World War II, prepared runways where large aircraft without skis can operate have predominated. The demand for prepared runways increased with the construction of the early warning sites in Greenland and the Antarctic phase of IGY in 1956. Presently, the large aircraft being used in polar operations are the C-124 (Globemaster) and the C-130 (Hercules), both with wheeled landing gear. The latter is also equipped with a ski-wheeled type modification for Greenland and Antarctic use; however, this reduces the load-carrying capacity. Since not all aircraft are equipped with skis the capability of landing wheeled aircraft on snow runways has become of considerable interest. In addition wheels are much lighter than skis, cause less drag on take off, and have no air drag. For ski-equipped aircraft longer runways are needed to lift the same amount of weight and air speed is lowered appreciably by air drag. A snow runway was constructed at Site II, Greenland, in 1955 and was successfully used for landing wheeled aircraft with cargo (C-124, C-47) and personnel (C-54) [2]. Similar attempts have been made in the Antarctic, but without success. It is the purpose of this paper to theoretically and experimentally analyze the problem of snow runways and establish criteria permitting adequate site evaluation and effective construction of landing strips. The results are applicable not only to polar regions but also to temperate areas with a heavy annual snow accumulation.