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On single particle breakage behavior of crushable weathered sands

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Journal of Mountain Science 2022年第12期19卷 3627-3644页

作者： yu fang-wei ZHAO Chuang LIU wei-chen Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610299China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China China-Pakistan Joint Research Centeron Earth Sciences Islamabad 45320Pakistan Department of Civil Engineering The University of TokyoTokyo 113-8656Japan Department of Civil Engineering Zhejiang UniversityHangzhou 310058China

This paper presents an experimental study on single particle breakage behavior of crushable weathered sands by a number of single particle uniaxial compression tests to comprehensively investigate the characteristics of single particle breakage,the probability of survival of single particle,and the effects of particle size and weathering on single particle *** behavior of single particle under uniaxial compression falls into the mixed five phases:damage by chipping,elastic deformation,fragmentation by partial fracture,breakage by splitting,and the residuals,demonstrating the complexity and variability of the tensile strengths of single *** behavior of single particle breakage was quantified herein by the initial fracture and failure strengths of single *** probability of survival decreased as the characteristic stresses *** increase in the particle size or weathering number of single particle resulted in a reduction in the probability of survival of single *** a given probability of survival,the difference in the initial fracture characteristic stress and failure characteristic stress decreased with increasing particle size but showed a complex change with increasing weathering *** probability of survival showed greater variability for the normalized initial fracture characteristic stress than for the normalized failure characteristic stress,implying that the initial fracture stresses of single particles diverged more than the failure stresses of the *** average initial fracture and failure characteristic stresses,and the initial fracture and failure characteristic stresses corresponding to 1/e(37%)survival of single particles decreased while increasing particle size or weathering number,but the decrease showed a sharper rate for smaller single particles with a lower weathering *** ln-ln coordinates showed a linear representation of the failure characteristic stress and particle size,verifying th

关键词： Breakage Compression Particle size Probability of survival Sands Weathering

Particle breakage and the mobilized drained shear strengths of sand

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Journal of Mountain Science 2016年第8期13卷 1481-1488页

作者： yu fang-wei SU Li-jun Institute of Mountain Hazards and Environment Chinese Academy of Sciences Department of Civil Engineering The University of Tokyo

This paper presents particle breakage and the mobilized drained shear strengths of sand with the purpose of clarifying the influence of particle breakage on the mobilized shear strengths of sand. Several drained triaxial tests were carried out on Silica sand No.5 under 3 MPa confining pressure to produce the pre-crushed sands in simulating the high- pressure shear process on soil to result in particle breakage, and then the pre-crushed sands were re- sheared in series of drained triaxial tests to investigate the mobilized strengths of the pre-crushed sands in detecting the influence of particle breakage. It was found that, by deteriorating strain-stress behavior, particle breakage resulted in change of stress-dilataney behavior in translation and rotation of the relation of the dilatancy factor and the effective principal stress ratio. For a given initial void ratio, particle breakage resulted in impairment of dilatancy behavior of soil to be more contractive in deterioration of the mobilized friction angle and the mobilized dilatancy angle and reduction of void ratio. However, particle breakage resulted in increase of the mobilized basic friction angle especially before failure. In addition, the influence of particle breakage on the mobilized strengths was revealed to be influenced by the shear stress-strain state.

关键词： Particle breakage Mobilized strengths Friction Dilatancy Void ratio Sand

Influence of grain segregation on the behavior of sand in triaxial tests

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Journal of Mountain Science 2021年第10期18卷 2776-2790页

作者： yu fang-wei PENG Xiong-zhi SU Li-jun Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China China-Pakistan Joint Research Center on Earth Sciences CAS-HECIslamabad 45320Pakistan University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering The University of TokyoTokyo 113-8656Japan Department of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China

As a common phenomenon in granular flow, grain segregation plays a great role in affecting the behavior of granular soil by causing a great change of grain-void distribution in granular soil. This paper presents an experimental study on the influence of grain segregation on the behavior of sand, by a number of triaxial tests to interpret the characteristic behavior, friction and dilatancy behavior, excess pore water pressure behavior and critical state behavior of sand incorporating grain segregation. An index-grain segregation index was proposed to quantify grain segregation. Grain segregation affected greatly the characteristic behavior of sand, causing the movement of void ratio-dilatancy relation of sand towards the increase of void ratio and dilatancy of sand. In the drained tests, the mobilized friction angle of sand showed a decrease followed by an increase but the mobilized dilatancy angle of sand increased, with increasing grain segregation index. An increase in grain segregation index impaired the basic friction of sand. In the undrained tests, the mobilized friction angle of sand showed an increase followed by a decrease with increasing grain segregation index. However, grain segregation caused an increase of the mobilized dilatancy of sand followed by a different development. An increase in grain segregation resulted in a higher summit of the dilatancy of sand but with a faster decrease along axial strain. In the q-p′ plane, grain segregation caused a reciprocating rotation of the dilatancy line and failure line of sand. Grain segregation resulted in enhancement of the peak-state dilatancy of sand, affecting greatly peakstate friction angle and peak-state basic friction angle of sand as well as the normalized excess pore water pressure. The excess friction angle of sand showed an increase followed by a decrease in the drained tests but increased linearly in the undrained tests, with increasing grain segregation index. The excess friction angle-over-maxim

关键词： Critical state Dilatancy Friction Grain segregation Landslides Soil behavior Triaxial tests

Influence of particle breakage on the isotropic compressibility of sands

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Journal of Mountain Science 2022年第7期19卷 2086-2099页

作者： yu fang-wei SU Li-jun PENG Xiong-zhi Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu610299China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing100101China China-Pakistan Joint Research Center on Earth Sciences Islamabad45320Pakistan University of Chinese Academy of Sciences Beijing100049China Department of Civil Engineering The University of TokyoTokyo113-8656Japan Department of Civil Engineering Southwest Jiaotong UniversityChengdu610031China

Particle breakage is a theme of great focus on affecting the behavior of granular *** paper presents an experimental investigation on the influence of particle breakage on the isotropic compressibility of the precrushed sands using a number of drained isotropic consolidation *** breakage resulted in movement of the compression lines followed by the rebound lines towards a decrease in the void ratio,implying that particle breakage caused a more contractive *** breakage impaired the bulk deformation modulus by increasing the compression coefficient for the compression behavior of the precrushed sands,but showed a complex effect on the bulk deformation modulus and rebound coefficient for the rebound behavior of the precrushed ***,particle breakage caused an increase in the compression indexes of the precrushed sands but showed a complex effect on the rebound indexes of the precrushed *** the e-p’plane and the e-logp’plane,the compression lines and rebound lines of the precrushed sands were curved.A generalized model was proposed to straighten the compression and rebound lines of the precrushed sands in the e-(p’p_(a))^(α) *** breakage resulted in a general rotation and translation of the linear compression and rebound lines of the precrushed sands in the e-(p’p_(a))^(α)*** critical state line and isotropic consolidation line on the loosest state of silica sand no.5 were curved in the e-logp’plane but straightened in the e-p’^(α=0.7) *** the e-p’^(α=0.7 )plane,a reasonable linear critical state line of silica sand no.5 was proposed by adjusting it to match the isotropic consolidation line on the loosest state.

关键词： Compression Isotropic consolidation Particle breakage Rebound Sands Triaxial tests

A back-propagation neural-network-based displacement back analysis for the identification of the geomechanical parameters of the Yonglang landslide in China

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Journal of Mountain Science 2017年第9期14卷 1739-1750页

作者： yu fang-wei PENG Xiong-zhi SU Li-jun Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China Department of Civil Engineering Southwest Jiaotong University Chengdu 610031 China CAS Center for Excellence in Tibetan Plateau Earth Sciences Bering 100101 China University of Chinese Academy of Sciences Beijing 100049 China

Xigeda formation is a type of hundredmeter-thick lacustrine sediments of being prone to triggering landslides along the trunk channel and tributaries of the upper Yangtze River in China. The Yonglang landslide located near Yonglang Town of Dechang County in Sichuan Province of China, which was a typical Xigeda formation landslide, was stabilized by anti-slide piles. Loading tests on a loading-test pile were conducted to measure the displacements and moments. The uncertainty of the tested geomechanical parameters of the Yonglang landslide over certain ranges would be problematic during the evaluation of the landslide. Thus, uniform design was introduced in the experimental design,and by which, numerical analyses of the loading-test pile were performed using Fast Lagrangian Analysis of Continua(FLAC3D) to acquire a database of the geomechanical parameters of the Yonglang landslide and the corresponding displacements of the loadingtest pile. A three-layer back-propagation neural network was established and trained with the database, and then tested and verified for its accuracy and reliability in numerical simulations. Displacement back analysis was conducted by substituting the displacements of the loading-test pile to the well-trained three-layer back-propagation neural network so as to identify the geomechanical parameters of the Yonglang landslide. The neuralnetwork-based displacement back analysis method with the proposed methodology is verified to be accurate and reliable for the identification of the uncertain geomechanical parameters of landslides.

关键词： Back-propagation neural network Displacement back analysis Geomechanical parameters Landslide Numerical analysis Uniform design Xigeda formation

Seismic stability analysis of slopes with pre-existing slip surfaces

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Journal of Mountain Science 2018年第6期15卷 1331-1341页

作者： SU Li-jun SUN Chang-ning yu fang-wei ALI Sarfraz Key Laboratory of Mountain Hazards and Earth Surface Process of Chinese Academy of Sciences Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beifing 100101 China University of Chinese Academy of Sciences Beijing 100049 China School ofAdvanced Geomechanieal Engineering （SAGE） and Research Center ofCPEC （RCC） National University of Sciences and Technology （NUST） Pakistan

In analyzing seismic stability of a slope with upper bound limit analysis method, the slip surface is often assumed as a log-spiral or plane slip surface. However, due to the presence of a weak layer and unfavorable geological structural surface or a bedrock interface with overlying soft strata, the preexisting slip surface of the slope may be irregular and composed of a series of planes rather than strictly logspiral or plane shape. A computational model is developed for analyzing the seismic stability of slopes with pre-existing slip surfaces. This model is based on the upper bound limit analysis method and can consider the effect of anchor bolts. The soil or rock is deemed to follow the Mohr-Coulomb yield criterion. The slope is divided into multiple block elements along the slip surface. According to the displacement compatibility and the associated flow rule, a kinematic velocity field of the slope can be obtained computationally. The proposed model allows not only calculation of the rate of external work owing to the combined effect of self-weight and seismic loading, but also that of the energy dissipation rate caused by the slip surface, interfaces of block elements and anchorage effect of the anchors. Considering a direct relationship between the rate of external work and the energy dissipation rate, the expressions of yield acceleration and permanent displacement of anchored slopes can be derived. Finally, the validity of this proposed model is illustrated by analysis on three typical slopes. The results showed that the proposed model is more easily formulated and does not need to solve complex equations or time consuming iterations compared with previous methods based on the conditions of force equilibrium.

关键词： Slope stability Pre-existing slip surface Seismic loading Limit analysis Yield acceleration Permanent displacement

Cloning and Expression of One Fibrinolytic Enzyme from Bacillus sp. zlw-2

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Agricultural Sciences in China 2009年第5期8卷 591-596页

作者： HAN Xin-mian GUO Run-fang yu Hong-wei JIA Ying-min Department of Biology Engineering Agricultural University of Hebei Baoding 071000 P.R.China

The gene encoding fibrinolytic enzyme from Bacillus sp. zlw-2 was cloned and sequenced （accession no. EU734749）, which was 1146 bp, encoded 381 amino acids and had 99% homology with Nattokinase YF308 and NAT. The genes encoding pre-pro-fibrinolytic enzyme （including signal peptide, propeptide, and mature peptide） and fibrinolytic enzyme （including mature peptide） were cloned into pET28a vector respectively and then transformed into Escherichia coli BL21 （DE3）. The recombinant ofpre-pro-fibrinolytic enzyme showed enzyme activity of 183 U mL^-1, while no detectable enzyme activity could be found from the recombinant of the mature peptide.

关键词： fibrinolytic enzyme Nattokinase clone recombinant expression

Experimental and theoretical study of mechanical properties of root-soil interface for slope protection

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Journal of Mountain Science 2020年第11期17卷 2784-2795页

作者： SU Li-jun HU Bing-li XIE Qi-jun yu fang-wei ZHANG Chong-lei Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101China China-Pakistan joint Research Center on Earth Sciences IslamabadPakistan University of Chinese Academy of Sciences Beijing 100049China

Plant roots mechanically enhance the strength of soil and improve slope stability through *** the popularization of ecological slope-protection technology,a quantitative study of how roots help to anchor soil is highly *** object of the present study is thus to investigate how roots and soil combine to affect the mechanical properties of the root-soil *** this end,pullout experiments of cedar roots of different diameters in soils of different density were *** experimental results show that the maximum pullout force increases significantly with increasing root diameter,but only slightly increases with increasing soil density,which indicates that the root diameter has a greater impact on the maximum pullout force than soil ***,based on studies of fiber-reinforced composites,a root-soil pull-out model was proposed to study the evolution of shear stress on root-soil *** approach ensures that the model accurately reflects the dynamic stress distribution evolution at the root-soil interface and can calculate the pullout process of embedded root from *** accuracy of the model is verified by comparing the calculated results with experimental ***,how soil density and root diameter affect the anchoring force was *** results indicate that the maximum anchoring force increases linearly with increasing root diameter,but nonlinearly with increasing soil density until reaching a fixed *** results show that the root soil pull-out model has significant practical value in slope protection.

关键词： Ecological slope-protection Anchoring force Pullout experiment Pullout model Model prediction

High specificity detection of Pb^2＋ ions by p-SCN-Bz-DTPA immunogen and p-NH2-Bn-DTPA coating antigen

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Frontiers of Environmental Science & Engineering 2014年第5期8卷 729-736页

作者： Ruozhen yu Zheng fang wei MENG Zhenguang YAN Lina DU Hong WANG Zhengtao LIU State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Sciences Beijing 100012 China

Only one bifunctional metal-chelator was used to prepare immunogen and coating antigen in all of the previous researches. However, the antibody-specific recognition to the spacer arm of the bifunctional metal- chelator might lower the specificity of heavy metal ions immunoassay. Two different bifunctional metal-chelators were adopted to prepare the immunogen and coating antigen respectively in our study to avoid this problem. The conjugates of keyhole limpet hemocyanin （KLH） and p-SCN-Bz-DTPA-Pb were used as immunogen, whereas the conjugates of bovine sentrn albumin （BSA） and p- NH2-Bn-DTPA-Pb were used as coating antigen. Poly- clonal antibodies specific to DTPA-Pb chelates were obtained from rabbits. Indirect competitive enzyme-linked immunosorbent assay （ELISA） was adopted to detect Pb^2＋ ion solutions prepared by Pb^2＋ standard solution and ultrapure water. In the mixing microplate, DTPA and Pb2＋ ions formed chelates and combined with specific anti- bodies. After incubation, the DTPA-Pb and the antibodies complex were added into the wells of the reaction microplate. The reaction microplate was coated by the conjugates ofBSA andp-NH2-DTPA-Pb, which competed for the specific antibodies. The result signals presented a good sigmoid curve when the Pb^2＋ concentration ranges from 0.01 to 100mg·L^-1 The IC50 of the indirect competitive ELISA is 0.23±0.04mg·L^-1 Pb2＋ ion. The cross-reaction with Cd^2＋, Cu^2＋, Fe^2＋, Mn^2＋, Zn^2＋, and other divalent ions were less than 5%.

关键词： p-SCN-Bz-DTPA p-NH2-Bn-DTPA leadion polyclonal antibody