Characterization of Spatial Variability of CPTU Data in a Liquefaction Site Improved by Vibro-compaction Method

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.

Evaluation of Geotechnical Parameters of a Lagoonal Clay Deposit in Jiangsu Lixia River Area of China by Seismic Piezocone Tests

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.

A structure-based approach to evaluation product adaptability in adaptable design

Qiang Cheng,Guojun Zhang,Zhifeng Liu,Peihua Gu,Ligang Cai 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.5

Adaptable design, as a new design paradigm, involves creating designs and products that can be easily changed to satisfy different requirements. In this paper, two types of product adaptability are proposed as essential adaptability and behavioral adaptability, and through measuring which respectively a model for product adaptability evaluation is developed. The essential adaptability evaluation proceeds with analyzing the independencies of function requirements and function modules firstly based on axiomatic design, and measuring the adaptability of interfaces secondly with three indices. The behavioral adaptability reflected by the performance of adaptable requirements after adaptation is measured based on Kano model. At last, the effectiveness of the proposed method is demonstrated by an illustrative example of the motherboard of a personal computer. The results show that the method can evaluate and reveal the adaptability of a product in essence, and is of directive significance to improving design and innovative design.

Engineering Properties and Microstructural Characteristics of Foundation Silt Stabilized By Lignin-based Industrial By-product

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.

Mechanical and Microscopic Properties of Copper-contaminated Soil Solidified with Calcium Carbide Residue, Metakaolin, and Desulfurization Gypsum under Freeze-thaw Cycles

Qiang Wang,Dandan Ge,Guojun Cai,Man Li,Liuyan Wu,Huangrui Xu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

The solidification/stabilization effect of heavy metal contaminated soils in frozen soil regions may be weakened. A novel binder comprising calcium carbide residue, metakaolin, and desulfurization gypsum was used to solidify and stabilize copper-contaminated soil subjected to freeze-thaw (F-T) cycles. The unconfined compressive strength (UCS), F-T cycles, scanning electron microscope (SEM), X-ray diffraction (XRD), and pH tests were conducted to investigate the characteristics of UCS, deformation, pH value, and microscopic mechanism of contaminated soils. The results demonstrated that the UCS of contaminated soils decreased with the increasing F-T cycles and Cu2+ concentration; the strength loss rate increased first and then decreased as the F-T cycles increased. The failure strain rose first and then reduced with the increase of F-T cycles, and increased with the rise of Cu2+ concentration. There was a considerable correlation between UCS, failure strain, and deformation modulus E50. The pH value decreased with the increasing F-T cycles and Cu2+ concentration. The microscopic characteristics indicated that the formation of hydrated calcium silicate and ettringite was the fundamental reason for the enhanced UCS. Besides, heavy metals could be solidified and stabilized by chemical precipitation, physical encapsulation, and ion exchange. The effect of F-T cycles could significantly damage the internal structure of contaminated soils, and the frost heaving force could loosen the soil skeleton structure, leading to the deterioration of the mechanical properties.

Study on the Mechanical Characteristics of Urban Sludge Solidified by Industrial Waste

Liuyan Wu,Qiang Wang,Dandan Ge,Huangrui Xu,Guojun Cai 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Urban sludge is an extensive volume with a prominent environmental impact. The researchexplored an application technology for converting urban sludge into a usable improved soilresource by using industrial waste, providing a new reference for the reuse of industrial waste. In this study, three industrial wastes, namely ground granulated blast slag, calcium carbideresidue, and desulfurized gypsum, were used as curing agents to solidify the urban sludge. Based on the unconfined compressive strength (UCS) test and chamber analysis, the effects ofcuring agent dosing and maintenance age of sludge-cured soil on the UCS and stress- strainwere studied. The results showed that with the increase of curing agent, the UCS of cured soilfirst increased and then decreased, and the breaking strain showed a decreasing trend. Theoptimum ratio of materials was sludge: calcium carbide residue: ground granulated blast slag:desulfurization gypsum = 100:15:15:5, record this material ratio as C15G15D5. Moreover,trials showed that C15G15D5 cured the sludge soil better than the cement alone, whichachieved the purpose of reusing the three industrial wastes and urban sludge. It was analyzedthat the hydrated calcium silicate (C-S-H), calcium aluminate (C-A-H) and ettringite (AFt) inthe hydration products were produced to make the soil skeleton stronger and enhance thestrength of the sludge-cured soil.

Petrogenesis of the late Mesozoic highly fractionated I-type granites in the Luanchuan district: implications for the tectono-magmatic evolution of eastern Qinling

Yunhui Zhang,Huawen Cao,Mo Xu,Shouting Zhang,Li Tang,Shiyan Wang,Qiuming Pei,Guojun Cai,Tong Shen 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.2

Late Mesozoic granites are extensively distributed in the Luanchuan district of eastern Qinling and can be divided into two types: Late Jurassic to Early Cretaceous granites (ore-related plutons) and Late Cretaceous granites (Laojunshan batholith). This study presents new geochemical and zircon U-Pb-Hf isotopic data from the Shibaogou and Yuku plutons to provide robust constraints on the petrogenesis and tectonic significance of the late Mesozoic granites in the Luanchuan district. Zircon U-Pb dating results yielded weighted mean 206Pb/238U ages of 149.1 ± 0.8 Ma and 150.5 ± 0.8 Ma, which were interpreted as the crystallization ages of the Shibaogou and Yuku plutons, respectively. We propose that the late Mesozoic granites contain high concentrations of SiO2 and alkali elements (Na2O + K2O) and feature metaluminous to weakly peraluminous characteristics. Enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements are observed. Mineralogical and geochemical evidence reveal that the late Mesozoic granites are highly fractionated I-type granites with fractional crystallization of feldspar, plagioclase and accessory minerals (e.g., apatite and titanite or magnetite). Based on the Hf composition, we suggest that the parental magmas of the ore-related plutons were derived from remelting of the Taihua and Xiong’er groups with minor contributions of mantle-derived materials and that the Laojunshan batholith was generated by the hybridization of ancient crust- (Kuanping group) and mantle-derived components. Collectively, the above arguments indicates a tectonic transition from compression to post-collisional extension during the late Mesozoic, that was likely triggered by the continental collision of the North China Block and the Yangtze Block, which generated numerous contemporaneous granites and Mo-W-Pb-Zn-Ag-Au poly-metallic deposits.