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Golf Course Construction and Renovation
Published in L.B. (Bert) McCarty, Golf Turf Management, 2018
Depending on the green design and elevation of the site, the subgrade will be built into the existing grade or cut into the subsoil. If the grade is to be cut into the subsoil, the stripped topsoil may be stockpiled for future construction, such as mounds adjacent to the green, or distributed over the fairway and rough. Usually, greens built into the existing grade are elevated, requiring outside fill material for the subgrade. Heavier soils, such as clays, are desirable for the subgrade since these are easily compacted to form a firm base that does not readily shift or settle. In either case, the subgrade must be compacted to prevent future settling that might create depressions or pockets of poor drainage or, in the event of a higher grade, droughty areas. This is accomplished with a power-driven vertical compactor (modified jackhammer), a vibratory plate, or with a water-filled mechanical roller operated in several directions across the subgrade.
Subgrades
Published in Burt G. Look, Earthworks, 2023
The subgrade is the material immediately below the pavement. This material may be natural, or improved through remove and replace, stabilisation or placement of geosynthetics. The depth of “subgrade” varies depending on the type of load applications and the pavement type. There are advocates for a singular definition of subgrade depth. Yet one should not expect the same subgrade depth specification for a highway, a local exit ramp, and a bike path. The depth for testing of “subgrades” for site investigation is different for quality control purposes. The subgrade stress varies with the type of pavement (rigid or flexible) and whether a dynamic or “static” load applies. The type of material, and whether reactive clays (Chapter 10), also influence the subgrade depth to be tested.
Chemical and physical means of modifying local materials for paving
Published in Maxwell Lay, John Metcalf, Kieran Sharp, Paving Our Ways, 2020
Maxwell Lay, Metcalf John, Sharp Kieran
Because of the nature and location of pavements, it is often not feasible to use the best possible materials in their construction a pavement. Commercial and technical compromises must often be made. One approach is to modify the sub-optimal materials to enhance their appropriate properties. At the other end of the spectrum, pavement and subgrade soils can be enhanced by processes broadly called soil stabilisation. The use of the term stabilisation is curious as the role of the associated processes is to enhance, rather than to stabilise. The use of bitumen and cement to bind stones together, as discussed in Chapters 13 and 17, lies at one end of the enhancement spectrum. Table 18.1 summarises the six common stabilisation methods.
Development of a temperature prediction model for asphalt pavements considering air temperature data of preceding hours
Published in International Journal of Pavement Engineering, 2022
Ashish Walia, Rajat Rastogi, Praveen Kumar, S. S. Jain
Pavement is a layered structure capable of withstanding the repetitive movement of wheel loads during its service life. However, the continuous application of (unanticipated) higher wheel loads on pavement structure may lead to its premature failure. The early deterioration may also happen due to harsh environmental conditions, improper drainage, and insufficient strength of the subgrade layer. Literature indicates that environmental factors like temperature and moisture content primarily affect pavement performance (Ali and Lopez 1996). Although a good design can substantially control the drainage effect, the temperature cannot be controlled through human intervention and thus needs to be addressed carefully. The temperature directly influences the characteristics and performance of the asphalt layer (topmost layer of the flexible pavement) in terms of its stress-absorbing behaviour or relative stiffness (Huang 2004). Therefore, determining pavement temperature in the Asphalt Concrete (AC) layer is important for its performance assessment. Performance assessment can be done through either destructive or non-destructive testing (NDT). The destructive testing includes the extraction of cores, whereas the NDT technique facilitates assessment without much affecting the structural integrity of the pavement. The NDT-based structural evaluation may be carried out using Benkelman Beam or Falling Weight Deflectometer (FWD) equipment.
Liquefaction resistance behaviours of gravel steel slag
Published in European Journal of Environmental and Civil Engineering, 2022
Liyan Wang, Lianbang Wu, Yan Tang, Binghui Wang, Ke Sun, Aimable Ishimwe
Sand and gravel are main building materials and often used in artificial reclamation, subgrade cushions, earth-rock dams, and for other purposes. However, the continuous increment of scarcity level of sand and gravel in recent years needs urgently a new geo-backfill material with good liquefaction resistance. Steel slag is a recycled industrial solid waste. The aged eight-month steel slag usually could be used as backfill material (Deng et al., 2017, Wu et al., 2019; Liu & Zhang, 2016; Pao et al., 2016; Wu, 2011). At present, the research results of the dynamic characteristics of steel slag mixed with other materials include the following: the dynamic shear modulus and damping ratio of steel slag and sand mixtures was investigated (Li et al., 2018); the properties of mixtures of steel furnace slag, coal wash, and rubber crumbs used as sub-ballast were evaluated (Indraratna et al., 2018); and the effects of rubber crumbs on the cyclic behaviour of steel furnace slag and coal wash mixtures were researched (Qi et al., 2018).
Resilient modulus estimation using in-situ modulus detector: performance and factors
Published in International Journal of Pavement Engineering, 2022
Sang Yeob Kim, Dong-Ju Kim, Jong-Sub Lee, Thomas H.-K. Kang, Yong-Hoon Byun
The subgrade under the road serves as a foundation for the upper layers of road infrastructure. Subgrade strength, which can be expressed as load-carrying capacity, is an important parameter for pavement design (Peraka and Biligiri 2020). The California bearing ratio (CBR) test is a widely used laboratory test for assessing subgrade strength under pseudo-static loading. Previously, the CBR of a subgrade was estimated using a dynamic cone penetrometer (DCP) (Kleyn 1975, Webster et al. 1992, Gabr et al. 2000). However, when designing pavements, the resilient modulus of subgrade, which is measured under repetitive loading, should be considered to represent the stress state in pavements under wheel loads. To determine the resilient modulus of subgrade, repeated load triaxial tests are conducted as recommended by the American Association of State Highway and Transportation Officials (AASHTO). Nevertheless, high-quality core samples are required for repeated load triaxial tests. Moreover, field stress states that can influence the resilient modulus estimation are unknown.