Abstract
The design of high fill embankments (HFEs) on the loess plateau requires proper foundation treatment methods and reasonable prediction of postconstruction settlement (PCS). In situ tests were carried out on a test section of the collapsible loess foundation of a high fill airport to assess the reinforcement effects of common treatment methods. Based on in situ monitored data, the spatial-temporal variations of the PCS of the HFE were investigated, with a simple empirical formula proposed for PCS prediction. The PCS increases linearly with the fill thickness, and the PCS rate varies exponentially with the fill rate. Two engineering recommendations were made to reduce differential PCS and water damage for the test site. The first is to combine the reinforcement methods to reduce PCS of the HFE, i.e., dynamic compaction for loess foundation with lower water content and gravel piles with stabilizers for that with higher water content. The second is to employ the dynamic compaction (DC), percussive compaction (PC), and vibration compaction (VC) to strengthen the fill to reach an average compaction degree above 0.93 and a water content close to the optimal.
Highlights
Northwest China is a mountainous area, with a growing demand for deep excavation and high fill projects, such as dams, airports, subgrades, and urban space construction, especially in the collapsible loess area [1]
E main conclusions are as follows: (1) e average bearing capacities of the foundation reinforced by the dynamic compaction (DC), vibrating sinking gravel pile (VSGP), plain soil compaction pile (PSCP), and vibration compaction (VC) + DC methods are 350 kPa, 400 kPa, 340 kPa, and 370 kPa, respectively, while the elastic moduli after reinforcement are 2.6, 2.3, 2.0, and 4.4 times those of the undisturbed soil, respectively. e effective treatment depth of the foundation by the DC method can reach 5–9 m
While the VSGP method has a deeper treatment depth, it is prone to collapse during drilling. e PSCP method is more feasible in reinforcing the deep collapsible loess foundation
Summary
Northwest China is a mountainous area, with a growing demand for deep excavation and high fill projects, such as dams, airports, subgrades, and urban space construction, especially in the collapsible loess area [1]. Collapsible loess is a special soil with a loose structure and high porosity, and the shear strength of unsaturated loess is high and the compressibility is low. Fill technology of high embankments, foundation treatment methods, and postconstruction settlement (PCS) control are widely concerned issues. E prototype tests, in situ monitoring, numerical methods, laboratory tests, model tests, fuzzy theory, and analytical solutions have been used to study the PCS and control technology in high fill embankment (HFE) projects [3,4,5,6,7,8,9,10,11]). Geotextile reinforcement and tirereinforced methods have been verified to improve the strength of the soil of embankments [14, 17]. e deep mixed columns with cement-fly ash-gravel piles (CFGs) are commonly used for ground improvement to treat the settlement of embankments [5, 13, 20, 22, 23]
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