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Li Q.,Oregon State University | Yang Z.,University of Alaska Anchorage | Yang Z.,State Key Laboratory of Frozen Soil Engineering
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2017

Frozen soils, including seasonally frozen soils and perennially frozen ground, or permafrost, exist extensively in Alaska and other cold regions. During past earthquakes, extensive damages were observed in pile foundations, and frozen ground appears to be the direct cause of at least some of those damages. This paper analyzes frozen soil lateral resistance and its effects on pile foundations during earthquakes based on the testing results on reinforced concrete-filled steel-pipe piles embedded in deep seasonally frozen silts under large deflection and recommends an analysis tool for seismic design practices. Pile performance data measured in the test-including bending moment and deflection-were used to back-calculate the p-y values for the top half-meter of frozen silt. A p-y curve for frozen silt is proposed based on the experimental data. Results from modeling the test pile using the proposed p-y curve agree well with the test results. The proposed curve was further validated by independent field test data. It is concluded that the proposed p-y curve is capable of modeling both seasonally frozen and perennially frozen silts in frozen soil-pile interaction analyses during short-term lateral loading. Recommendations are provided on how to select soil parameters for constructing frozen-silt p-y curves. © 2016 American Society of Civil Engineers.


Gu Q.,State Key Laboratory of Frozen Soil Engineering | Gu Q.,Xiamen University | Yang Z.,University of Alaska Anchorage | Peng Y.,Xiamen University
Cold Regions Science and Technology | Year: 2016

In cold regions, accurately simulating the nonlinear responses of frozen soil-structure interaction (SSI) systems is of significant importance for the seismic safety assessment. This paper presents a finite element (FE) simulation of nonlinear lateral responses of a real reinforced-concrete filled steel pipe pile embedded in frozen ground at an outdoor test site in Fairbanks, Alaska. A pressure-independent multi-yield surface J2 plasticity model is used to simulate the frozen soil behavior, while frame element with fiber section and nonlinear steel/concrete model are used for the pile. The FE analysis results agree well with the experiment results. Furthermore, the response sensitivities to various material parameters are computed by using an efficient and accurate gradient computation method, i.e., direct differentiation method (DDM), with limited additional computational cost. Based on DDM, the relative importance of material parameters on system responses is studied when the system is subjected to varying lateral deflections, respectively (corresponding to different levels of lateral loads such as earthquakes). Stiffness-related parameters are dominant when the system is subject to small deflections, while strength-related or post-yield parameters become dominant for large deflections. In addition, global responses are slightly more sensitive to material parameters of pile than the parameters of frozen soil. The response sensitivity to the unfrozen soil below the frozen ground crust is almost negligible. Finally, the response sensitivities to the soil parameters are observed to decrease when the distance of the soil from the pile increases. The sensitivity analysis methodology presented in this paper can be adapted to other frozen soil-pile interaction cases and the study results provide valuable insight for engineering practice. © 2015 Elsevier B.V.


Lina Z.,Harbin Institute of Technology | Zheng W.,Harbin Institute of Technology | Shuang L.,Harbin Institute of Technology | Shuang L.,State Key Laboratory of Frozen Soil Engineering
Revista Romana de Materiale/ Romanian Journal of Materials | Year: 2016

The leaching behaviour of hydraulic concrete can't be ignored for its long-term exposure to surrounding water resulting in irreversible damage of durability, such as strength loss and porosity increase. The coupled effect of leaching and freeze-thaw cycles on the durability of hydraulic concrete in severe cold regions is a bigger challenge. For the quite slow process of natural leaching, electrochemical accelerated leaching method (EALM) was proposed to investigate the damage evolution under two test schemes (scheme one is only leaching for 50 days and scheme two is first 100 rapid freeze-thaw cycles and then leaching for 50 days) designed in this work. The electrical resistivity and calcium oxide dissolved mass were measured through electrode impedance spectroscopy (EIS) and EDTA titration method, respectively. Based on electrical resistivity measurement, the measurable damage can be discussed during above-mentioned single and coupled tests. The results indicate that compared with single leaching the coupled leaching with the freeze-thaw cycling leads to over 50% electrical resistance loss, the largest difference of both calcium oxide dissolved mass and pH in cathode room on the 21st day. © 2016, Procema SA. All rights reserved.


Gao L.,Dalian Nationalities University | Gao L.,Dalian University of Technology | Gao L.,State Key Laboratory of Frozen Soil Engineering | Luan M.,Dalian University of Technology | Li S.,Tianjin Institute of Urban Construction
Journal of Convergence Information Technology | Year: 2011

The original microstructure parameters were obtained from the SEM images derived from loess specimens before and after collapsing. Analysis of correlation between these parameters was made by correlation analysis in mathematical statistics. Principle component analysis is introduced to construct synthesis parameters. According to studies on a swatch composed by 21 loess SEM images and principal component contribution, it is indicated that some original parameters of loess microstructure are obviously correlation with others. That is, when describing the characteristics of loess microstructure with these parameters, superposition of information is clear. The results also indicted that three principle component can represent 96% information of nine original parameters. So using a reasonable number of principle components constructed by principal component analysis can greatly reduce the dimension of microstructure parameters. Principle component index can be used to establish the constitutive relationship to evaluate the collapsible deformation behavior of loess, which can reflect the inherent relation between microstructure and macro engineering properties, thus the paper lays down the groundwork for quantitative study on loess microstructure.


Liu X.,Southwest Jiaotong University | Zhu Z.,Southwest Jiaotong University | Zhu Z.,State Key Laboratory of Frozen Soil Engineering | Kang G.,Southwest Jiaotong University | Cai L.,Southwest Jiaotong University
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2012

The uniaxial time-dependent cyclic of carbon fiber/polyether ether ketone(PEEK) composite was studied experimentally. The volume fraction of carbon fiber was 30%. The property under stress-control led and stress-controlled loading and the ratcheting behaviors of carbon fiber/PEEK composite were discussed under different conditions. It was shown that the creep behavior of carbon fiber/PEEK composite is better than that of PEEK. In the experiment of strain-controlled cyclic, the stress amplitude has a close relationship with the applied strain loading rate and strain amplitude. Due to the stress relaxation, the responded stress amplitude will decreases as the hold time at strain peak increase. The ratcheting occurs in the composite to asymmetrical stress-controlled, and the ratcheting strain depends on the stress amplitude and stress loading rate. The stress holding time and low loading rate lead to an increased ratcheting strain. The carbon fiber will fail as the peak holding time beyond the range.


Zhu Z.-W.,Southwest Jiaotong University | Zhu Z.-W.,State Key Laboratory of Frozen Soil Engineering | Ning J.-G.,Beijing Institute of Technology | Liu X.,Southwest Jiaotong University
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2011

The test of the impact characteristic of soil is made on split Hopkinson pressure bar at various strain-rates. The dynamic mechanics properties and the strain-rate effect of soil are discussed. Based on the characteristics of measured dynamic stress-strain curves, as well as preparatory simulation, a new viscoelastic damage model has been introduced. A linear spring is put to parallel to two Maxwell units with different relaxing time to express distinct plastic flow. In the constitutive model, one Maxwell unit with low relaxing time is used to describe the low strain-rate response of soil; and the other one with high relaxing time is used to describe the high strain-rate response of soil. Simulated stress-strain curves using the model is of good consistency with measured curves, and the simulated parameters indicate that the response of the low strain-rate of soil is just the same as that of concrete. However, the response of the high strain-rate of soil is much more violent than that of concrete.


Yang Y.-G.,Shanxi University | Yang Y.-G.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Xiao H.-L.,Shanxi University | Zou S.-B.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | And 5 more authors.
Environmental Earth Sciences | Year: 2012

Investigation of water sources and flow pathways is crucial to understand and evaluate the characteristics of surface water and groundwater systems. This article aims to identify the hydrochemical and hydrological processes in different landscape zones based on hydrochemical analyses of various samples, including samples from glacier, snow, frozen soil meltwater, surface water, groundwater, and precipitation, in the alpine cold region of China. Hydrochemical tracers indicated that chemical compositions are characterized by the Ca-HCO3 type in the glacier-snow zone; the Mg-Ca-SO4 type in the alpine cold desert zone; the Ca-HCO3-SO4 type in the marsh meadow zone; the Ca-Mg-HCO3 type in the alpine shrub zone; and the Ca-Na-SO4 type in the mountain grassland zone. An end-member mixing model was used for hydrograph separation. The results showed that the Mafengou River in the wet season was recharged by groundwater in the alpine cold desert and alpine shrub zones (67%), surface runoff in the glacier-snow zone (11%), surface runoff in the alpine cold desert zone (8%), thawed water from frozen soil in the marsh meadow and mountain grassland zones (9%), and direct precipitation on the river channel (5%). This study suggests that precipitation from the whole catchment yielded little direct surface runoff; precipitation was mostly transformed into groundwater or interflow and was then concentrated into the river channel. This study provides a scientific basis for evaluation and management of water resources in the basin. © Springer-Verlag 2011.


Yang Y.,Shanxi University | Yang Y.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Xiao H.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Wei Y.,University of Melbourne | And 5 more authors.
Hydrological Processes | Year: 2012

Studies on hydrological processes are often emphasized in resource and environmental studies. This paper identifies the hydrological processes in different landscape zones during the wet season based on the isotopic and hydrochemical analysis of glacier, snow, frozen soil, groundwater and other water sources in the headwater catchment of alpine cold regions. Hydrochemical tracers indicated that the chemical compositions of the water are typically characterized by: (1) Ca-HCO 3 type in glacier snow zone, (2) Mg-Ca-SO 4 type for surface runoff and Ca-Mg-HCO 3 type for groundwater in alpine desert zone, (3) Ca-Mg-SO 4 type for surface water and Ca-Mg-HCO 3 type for groundwater in alpine shrub zone, and (4) Ca-Na-SO 4 type in surface runoff in the alpine grassland zone. The End-Members Mixing Analysis (EMMA) was employed for hydrograph separation. The results showed that the Mafengou River in the wet season was mainly recharged by groundwater in alpine cold desert zones and shrub zones (52%), which came from the infiltration and transformation of precipitation, thawed frozen soil water and glacier-snow meltwater. Surface runoff in the glacier-snow zone accounted for 11%, surface runoff in alpine cold desert zones and alpine shrub meadow zones accounted for 20%, thawed frozen soil water in alpine grassland zones accounted for 9% of recharge and precipitation directly into the river channel (8%). This study suggested that the whole catchment precipitation did not produce significant surface runoff directly, but mostly transformed into groundwater or interflow, and finally arrived in the river channel. © 2011 John Wiley & Sons, Ltd.


Wang F.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Xiao H.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Zou S.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Zou S.,State Key Laboratory of Frozen Soil Engineering
Environmental Earth Sciences | Year: 2012

This research on an alluvial plain oasis in the middle reaches of the Heihe River used the trend estimation model of principal component analysis through fixed position experiments to investigate and analyze changes in saline meadow soil characteristics after reclamation of the oasis. The conclusion is that after cultivation for a number of years, clay content increased from 9. 18% (before cultivation) to 12. 93% (after 30 years of cultivation) and soil nutrient content increased as well, but available potassium decreased from 1,315. 50 mg/kg (before cultivation) to 240. 84 mg/kg (after 30 years of cultivation). As a result of engineering, biological, and agricultural methods, total salt content significantly decreased by 97. 15% from 70. 28 g/kg (before cultivation) to 2. 00 g/kg (after 30 years of cultivation). Through the trend estimation model of principal components analysis (PCA), it was found that soil quality improved over time. Synthetic analysis of various indexes of soil quality revealed that meadow saline soil could be used for agricultural production with responsible tillage. © 2011 Springer-Verlag.


Nan Z.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Nan Z.,State Key Laboratory of Frozen Soil Engineering | Huang P.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Zhao L.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute
Acta Geographica Sinica | Year: 2013

In this study, an extended surface frost number model (E-FROSTNUM) is applied to simulate the spatial distribution of permafrost in the study area combined with remotely sensed data and available field survey data from an ongoing project titled Permafrost Background Investigation over the Qinghai-Tibet Plateau. The distribution simulation is verified with the two typical areas investigated during the project. Moreover, a relationship between soil temperatures at a 10-m depth and topographic factors (latitude/longitude, elevation, aspect) and potential incoming solar radiation is found to be significant and applicable to estimate soil temperature at the 10-m depth in the study area. Based on this estimation, the permafrost depths are computed using a regressed relationship of 10 m soil temperature and permafrost bottom depth, derived from the west Kunlun borehole records. The study shows that 36.9% of the area is covered by permafrost and mainly distributed in the areas of Karakoram and western Kunlun Mountains in a range of 34°~36.5°N, and 57.5% covered by seasonally frozen soil, which includes the Tarim Basin and the area south of 34°N.

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