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Gang Liu
MOE Key Laboratory of High-speed Railway Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan, China

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Review
Published: 23 December 2020 in Nanomaterials
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Since the concept of sustainable development enjoys popular support in the 21st century, various kinds of unconventional materials were introduced for soil improvement in the past few decades to replace the traditional materials like concrete and lime. This paper compared nanomaterials with other three kinds of representative unconventional materials to demonstrate its superiority in soil treatment. The other three kinds of unconventional materials include microbially induced calcite precipitation (MICP), recycled tire and environmental fiber. Nanomaterial and MICP have a comprehensive effect on soil reinforcement, since they can improve shear strength, adjust permeability, resist liquefaction and purify the environment. Recycled tire and environmental fibers are granular materials that are mostly adopted to reinforce reconstituted soil. The reinforcement mechanisms and effects of these four kinds of unconventional materials are discussed in detail, and their price/performance ratios are calculated to make an evaluation about their market application prospects. It can be seen that nanomaterials have promising prospects. Colloidal silica, bentonite and laponite present a satisfactory effect on liquefaction mitigation for sandy foundation, and carbon nanotube has an aptitude for unconfined compressive strength improvement. Among the investigated nanomaterials, colloidal silica is the closest to scale market application. Despite the advantages of nanomaterials adopted as additives for soil improvement, they are known for unwanted interactions with different biological objects at the cell level. Nevertheless, research on nanomaterials that are adopted for soil improvement are very promising and can intensify the relationship between sustainable development and geotechnical engineering through innovative techniques.

ACS Style

Gang Liu; Chong Zhang; Mingzhi Zhao; Wenbo Guo; Qiang Luo. Comparison of Nanomaterials with Other Unconventional Materials Used as Additives for Soil Improvement in the Context of Sustainable Development: A Review. Nanomaterials 2020, 11, 15 .

AMA Style

Gang Liu, Chong Zhang, Mingzhi Zhao, Wenbo Guo, Qiang Luo. Comparison of Nanomaterials with Other Unconventional Materials Used as Additives for Soil Improvement in the Context of Sustainable Development: A Review. Nanomaterials. 2020; 11 (1):15.

Chicago/Turabian Style

Gang Liu; Chong Zhang; Mingzhi Zhao; Wenbo Guo; Qiang Luo. 2020. "Comparison of Nanomaterials with Other Unconventional Materials Used as Additives for Soil Improvement in the Context of Sustainable Development: A Review." Nanomaterials 11, no. 1: 15.

Journal article
Published: 25 June 2020 in Transportation Geotechnics
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This paper presents a practical method for identifying the fundamental design parameters of a multilayered earth structure in ballastless tracks at an operational speed of 400 km/h. The properties of subgrade materials and layer thickness are determined based on vehicle–track coupled dynamic numerical analysis and integrated empirical models incorporating a threshold cyclic strain approach. The principle of the proposed method is to limit train-induced strain and deformation in the foundations in order to achieve satisfactory long-term track performance. Firstly, the critical velocity effect is introduced and briefly assessed for design purposes. Dynamic amplification factor (DAF) is obtained from the statistical analysis of simulated results of vertical vehicle–track coupled dynamic models. A trapezoidal stress pattern is used to characterize the mobilized stress distribution on the subgrade surface under two-axle moving loads of a vehicle on a slab track. The attenuation law of excess vertical soil stress in a substructure under traffic loads is consequently reproduced using Boussinesq’s equation. Next, two threshold strains are defined in accordance with the accumulation rate of residual subgrade settlement, predicted by empirical models as a function of the K30 value (modulus of subgrade reaction) and plasticity index of the subgrade aggregate. Following this, the abovementioned results are synthesized into design criteria that can be readily utilized. The application of the proposed method is illustrated by an example of earthwork design. Field observations are finally presented for the validation of the developed approach. The design methodology will improve knowledge of slab track substructure design and is expected to extend the applicability of the current railway code to higher train speed conditions.

ACS Style

Tengfei Wang; Qiang Luo; Jiankun Liu; Gang Liu; Hongwei Xie. Method for slab track substructure design at a speed of 400 km/h. Transportation Geotechnics 2020, 24, 100391 .

AMA Style

Tengfei Wang, Qiang Luo, Jiankun Liu, Gang Liu, Hongwei Xie. Method for slab track substructure design at a speed of 400 km/h. Transportation Geotechnics. 2020; 24 ():100391.

Chicago/Turabian Style

Tengfei Wang; Qiang Luo; Jiankun Liu; Gang Liu; Hongwei Xie. 2020. "Method for slab track substructure design at a speed of 400 km/h." Transportation Geotechnics 24, no. : 100391.

Review
Published: 18 December 2019 in Applied Sciences
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In the booming field of nanotechnology, colloidal silica (CS) has been introduced for ground improvement and liquefaction mitigation. It possesses a great ability to restrain pore pressure generation during seismic events by using an innovative stabilization technique, with the advantages of being a cost-effective, low disturbance, and environmentally friendly method. This paper firstly introduces molecular structures and some physical properties of CS, which are of great importance in the practical application of CS. Then, evidence that can justify the feasibility of CS transport in loose sand layers is demonstrated, summarizing the crucial factors that determine the rate of CS delivery. Thereafter, four chemical and physical methods that can examine the grouting quality are summed and appraised. Silica content and chloride ion concentration are two effective indicators recommended in this paper to judge CS converge. Finally, the evidence from the elemental tests, model tests, and field tests is reviewed in order to demonstrate CS’s ability to inhibit pore water pressure and lower liquefaction risk. Based on the conclusions drawn in previous literature, this paper refines the concept of CS concentration and curing time being the two dominant factors that determine the strengthening effect. The objective of this work is to review CS treatment methodologies and emphasize the critical factors that influence both CS delivery and the ground improving effect. Besides, it also aims to provide references for optimizing the approaches of CS transport and promoting its responsible use in mitigating liquefaction.

ACS Style

Mingzhi Zhao; Gang Liu; Chong Zhang; Wenbo Guo; Qiang Luo. State-of-the-Art of Colloidal Silica-Based Soil Liquefaction Mitigation: An Emerging Technique for Ground Improvement. Applied Sciences 2019, 10, 15 .

AMA Style

Mingzhi Zhao, Gang Liu, Chong Zhang, Wenbo Guo, Qiang Luo. State-of-the-Art of Colloidal Silica-Based Soil Liquefaction Mitigation: An Emerging Technique for Ground Improvement. Applied Sciences. 2019; 10 (1):15.

Chicago/Turabian Style

Mingzhi Zhao; Gang Liu; Chong Zhang; Wenbo Guo; Qiang Luo. 2019. "State-of-the-Art of Colloidal Silica-Based Soil Liquefaction Mitigation: An Emerging Technique for Ground Improvement." Applied Sciences 10, no. 1: 15.

Journal article
Published: 05 April 2019 in Applied Sciences
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To investigate the evolving characteristics of plastic deformation for the angular gravels that are used to construct subgrade bed, a laboratory model test is performed with cyclic load applying. Vertical deformation is measured in real time by displacement transducers and further modified to analyze the plastic behavior of model fillings. It can be found that vertical plastic deformation shows quite different developing patterns under the effect of different cyclic amplitudes for a given model. A power function is adopted to describe the relationship between deformation rate and loading times. By analyzing the value of the power exponent and the corresponding developing features of plastic deformation rate, model filling status can be classified into four different zones, i.e., rapid stabilization, tardy stabilization, tardy failure, and rapid failure. Such a classification reveals different developing patterns of plastic deformation and satisfies the design of subgrade bed for ballasted and unballasted railway.

ACS Style

Gang Liu; Mingzhi Zhao; Qiang Luo; Hongyu Jia. Effect of Cyclic Load Amplitude on the Evolving Characteristics of Accumulative Deformation in Subgrade Bed. Applied Sciences 2019, 9, 1435 .

AMA Style

Gang Liu, Mingzhi Zhao, Qiang Luo, Hongyu Jia. Effect of Cyclic Load Amplitude on the Evolving Characteristics of Accumulative Deformation in Subgrade Bed. Applied Sciences. 2019; 9 (7):1435.

Chicago/Turabian Style

Gang Liu; Mingzhi Zhao; Qiang Luo; Hongyu Jia. 2019. "Effect of Cyclic Load Amplitude on the Evolving Characteristics of Accumulative Deformation in Subgrade Bed." Applied Sciences 9, no. 7: 1435.