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RISS 인기검색어
- 검색키워드
- 저자 : Anand J. Puppala (검색결과 4 건)
- 무료
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Guojun Cai,Songyu Liu,Anand J. Puppala 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.5
The use of the Seismic Piezocone Test (SCPTU) in geotechnical site investigation offers field assessment on stratigraphy and soil behavior. Compared with some traditional investigation methods such as drilling, sampling and field inspecting method or laboratory test procedures, SCPTU can greatly accelerate the field work and hereby reduce corresponding operation cost. The results of a site investigation on the soft, normally to slightly overconsolidated, Lixia River lagoonal clay deposit underlying several expressway lines, including a seismic piezocone penetration test, undisturbed sampling from an adjacent borehole, and laboratory testing, are reported. The determination of soil profile and the main geotechnical properties is facilitated by the use of seismic piezocone penetration test that can provide up to four independent reading with depth from a single sounding. The coupled use of normalized cone resistance and pore pressure parameter provides a simple and quick soil classification for highly interbedding of Lixia River lagoon ground. Comparison of the results reveals the validity of SCPTU tests to interpret the engineering properties of Lixia River lagoonal clay. These data will also be particularly useful for future local construction work.
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Guojun Cai,Jun Lin,Songyu Liu,Anand J. Puppala 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1
Vibro-compaction is a ground improvement technique in which the weak or loose soil deposits are compacted by the vibrating probe or vibroflot penetration. The Piezocone Penetration Test (CPTU) has been found to be one of the best methods to assess the effect of ground improvement due to its continuous, reliable and repeatable data collected. The spatial variability of a liquefactionsusceptible site improved by vibro-compaction was assessed using random field theory. The CPTU soundings were conducted to characterize the variation of random field model parameters. Given the relatively high data frequency of the cone tip resistance in vertical direction, the vertical random field parameters are determined with the modified Bartlett random field estimation procedure. Due to the lack of data in horizontal direction, the horizontal random field parameters are evaluated using a less rigorous way of the autocorrelation. It is shown that the normalized cone resistance is a well estimator of spatial variability. The statistical results suggest that both Scale of Fluctuation (SOF) and the Coefficient of Variation (COV) varied in different way after vibro-compaction.
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Tao Zhang,Guojun Cai,Songyu Liu,Anand J. Puppala 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.7
This paper presents details of a study that deals with determination of engineering properties and microstructural characteristics of a foundation soil (silt) sedimented in Jiangsu Province of China when it is stabilized by lignin-based industrial by-product. A series of laboratory tests were carried out with respect to evaluate the effect of lignin content and curing time on the overall soil properties including Atterberg limits, pH, unconfined compressive strength, stress-strain characteristics, secant modulus, and California bearing ratio. In addition, scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry studies were conducted to understand the microstructural characteristics and stabilization mechanism of the stabilized silt. The results reveal that lignin has a great potential to improve engineering properties of silt and shows a promising prospect as a new environmentally friendly soil stabilizer. Curing time and lignin content have significant influence on the basic engineering properties and microstructural characteristics of the lignin stabilized silt. The optimum content of lignin for foundation silt in Jiangsu Province of China is approximately 12%. The precipitated cementing material is formed after stabilization of lignin with a period of curing. The stabilized silt switches over its response from a brittle to ductile material in the presence of lignin. Peak analysis results of the pore-size distribution curves demonstrates that the lignin stabilized silt exhibits bimodal behavior when the lignin content less than 8%, whereas it displays unimodal type when the lignin content is more than or equal to 8%. These observations provide enhanced understanding of lignin-based industrial by-product as a soil stabilizer at the foundation construction.
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Numerical analysis of geocell reinforced ballast overlying soft clay subgrade
Saride, Sireesh,Pradhan, Sailesh,Sitharam, T.G.,Puppala, Anand J. Techno-Press 2013 Geomechanics & engineering Vol.5 No.3
Geotextiles and geogrids have been in use for several decades in variety of geo-structure applications including foundation of embankments, retaining walls, pavements. Geocells is one such variant in geosynthetic reinforcement of recent years, which provides a three dimensional confinement to the infill material. Although extensive research has been carried on geocell reinforced sand, clay and layered soil subgrades, limited research has been reported on the aggregates/ballast reinforced with geocells. This paper presents the behavior of a railway sleeper subjected to monotonic loading on geocell reinforced aggregates, of size ranging from 20 to 75 mm, overlying soft clay subgrades. Series of tests were conducted in a steel test tank of dimensions $700mm{\times}300mm{\times}700mm$. In addition to the laboratory model tests, numerical simulations were performed using a finite difference code to predict the behavior of geocell reinforced ballast. The results from numerical simulations were compared with the experimental data. The numerical and experimental results manifested the importance that the geocell reinforcement has a significant effect on the ballast behaviour. The results depicted that the stiffness of underlying soft clay subgrade has a significant influence on the behavior of the geocell-aggregate composite material in redistributing the loading system.
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