Papers by Author: Jun Wang

Abstract: Shaking table test is an important means of simulated earthquake in laboratory, slope shaking table test data provide a scientific basis for analysis of dynamic stability and instability mechanism of slopes. Sine vibration table test data processing is different from general frequency domain analysis method, need real-time data processing in time domain. Taking the sine sweep test conditions, which is one of the conditions in "Earthquake landslide and slope prevention and control technology research on shaking table test", as an example. Describes the layout of sensors in shaking table test and the reasons; Sine sweep test load and aim; and listed the steps and methods of the sine sweep test in data processing; Through the processing and analysis of test data identified the vibration frequency of model and shaking table system is 30Hz, damping ratio is 2.06%; Analysis and calculation of the different sections of the slope and position of the amplification coefficient. A methodological guidance for shaking table test and dynamic response analysis of the slope is provided.

Abstract: The strong effect on ground damage and the serious earthquake-induced geological disasters are notable features of MS8.0 Wenchuan earthquake. This study obtained 993 earthquake geological disasters in Wudu District and Wenxian County of Gansu Province, by combining field investigation and interpretation of remote-sensing images. Then the characteristics of these geological disasters were investigated statistically using GIS techniques to determine how the occurrence of geological disasters correlated with intensity, distance from the rivers, slopes and elevations. The main results can be summarized as follows: (1) the geological disasters density increased with the increase of earthquake intensity; (2) the geological disasters triggered by earthquake show the feature of zonal distribution along the rivers; (3) the slope steepness is the main factor which controls the development of earthquake-induced geological disasters and most of the geological disasters are distributed with the slopes of 10 to 40 degree; (4) the earthquake-induced geological disasters have corresponding relationships with elevations, and most disasters occur with the elevation of 1000 to 2000 m.

Abstract: On the basis of the dynamic triaxial liquefaction test of the loess samples which were taken from the Shibei tableland, Guyuan city, and evaluating the liquefaction potential of the loess through laboratory experiment and response analysis. Then the liquefaction characteristics of saturated undisturbed loess under different level of liquefaction are analyzed based on the evaluation results. The results are shown that: when the saturated undisturbed loess liquefaction is light, dynamic stress is decayed barely, weak dynamic residual deformation is generated, pore water pressure begins to grow, the dynamic stress dynamic strain stagnant curves have not marked change, and the deformation of the soil is at viscoelastic stage. When the loess liquefaction is middling, attenuation of dynamic stress is not obviously, dynamic strain is increasing, amount of pore water pressure much higher than stage one, the long axis slope of hysteresis curves is reduced significantly, the sizes and shapes difference of adjacent hysteresis loop is obvious, and the deformation of the soil is at viscoelastic-plastic stage. When the loess is liquefied completely, dynamic stress is decayed evidently, dynamic strain increased dramatically, and its crest value could exceed 10%, the peak value of pore water pressure is sustainable increasing, and emerge the apparent fluctuation under the action of a drastic dynamic strain, the form of the stagnant curves tend to be irregular, the loess is in elastic-plastic stage.

Abstract: Based on Mohr - Coulomb failure criterion, dynamic strength characteristic of undisturbed loess in Xining, Lanzhou, Xiji and Xian was studied through dynamic triaxial test. And the regional characteristics of void ratio, natural moisture content, plasticity index and dynamic shear strength with different vibration frequency and natural conditions were analyzed. The research shows that dynamic shear strength of loess increases when consolidation stress rises under the same water content condition. However the increase trend is not proportional relationship. Initial void ratio and water content of loess under natural state rises from northwest to southeast, and dynamic cohesive force enhances. On the contrary, internal friction angle decreases with the change of characteristic. With the increasing trend of disturbed loesss clay content from northwest to southeast, dynamic cohesive force increases and internal friction angle decreases in the different amplitude. The conclusion enriches and develops the evaluation theory of loess regional dynamic characteristic and it is a universal method to reduce cost of different loess regional classification.

Abstract: Environment pollution and exhaustion of mineral resources aroused strongly research and development of fly ash utilization. As a kind of foundation treatment method, improved by fly ash is more and more used in highway, railway roadbed construction. With the increase of speed of vehicles and vehicle load, the influence of dynamic load on the subgrade has caused people's concern. In this paper, based on fly ash modified loess, dynamic property of modified fly ash loess is discussed through the dynamic triaxial test of the unsaturation disturbed loess. The effect of the dynamic elastic modulus and the damping ratio with different amount of fly ash loess is studied. The results show that the difference of dynamic properties in dynamic load and static load is large. It mainly presents the hysteresis quality and nonlinear relationship between dynamic stress and dynamic strain. And the dynamic elasticity modulus increases with fly ash mixed amount.

Abstract: Use of Seed’s simplified liquefaction evaluation method, combined with the dynamic triaxial test results, and the wave velocity of site liquefaction, to evaluate liquefaction potential of the four typical loess sites under the action of different seismic magnitudes, and calculate the boundary depth of the liquefaction site. Moreover, give the corresponding relationship between the typical loess site liquefaction boundary depth and shear wave velocity, and get the critical shear wave velocity of typical loess liquefaction site. The results of the study show that, (1) saturated loess site could be liquefied under the action of a certain intensity earthquake. (2) saturated soil layers which do not produce liquefied under the action of 6.5 degree earthquake, its critical shear wave velocity is about 227 m/s, and under the action of 7 degree earthquake its critical shear wave velocity is about 303 m/s, under the action of 8 degree earthquake its critical shear wave velocity is about 379 m/s. This conclusion enriches and develops the basis of liquefaction potential evaluation in the loess region.

Abstract: Use of Seed’s simplified liquefaction evaluation method, combined with the dynamic triaxial test results, and the wave velocity of site liquefaction, to evaluate liquefaction potential of the three typical loess sites under the action of different seismic magnitudes, and calculate the boundary depth of the liquefaction site. Moreover, give the corresponding relationship between the typical loess site liquefaction boundary depth and shear wave velocity, and get the critical shear wave velocity of typical loess liquefaction site. The results of the study show that, (1) saturated loess site could be liquefied under the action of a certain intensity earthquake. (2) saturated soil layers which do not produce liquefied under the action of 6.5 degree earthquake，its critical shear wave velocity is about 200 m/s, and under the action of 7 degree earthquake its critical shear wave velocity is about 303 m/s, under the action of 8 degree earthquake its critical shear wave velocity is about 368 m/s. This conclusion enriches and develops the basis of liquefaction potential evaluation in the loess region.

Abstract: By using the DSD-160 dynamic triaxial apparatus, liquefaction experiments under random seismic loading of the saturation original samples from a passenger rail line which located in the loess tableland in china was tested. Based on the test results, connected with the forecasting method of the liquefaction test under random seismic loading and the results of seismic hazard analysis, the liquefaction potential of the saturation loess from different regions in the passenger rail line is distinguished. Moreover, the predictions include 50 years probability of exceedance 10% and 2%of the loess liquefaction potential of the sites mentioned above is obtained.

Abstract: In this paper, the effects of the main property indexes on the saturation original loess liquefaction is analyzed through the dynamic triaxial test by using the WF-12440 testing system, combined with the experimental results, the influence of density-grain degree coupling on saturated loess liquefaction is comprehensively analyzed. The result shows that the influence of density-grain degree coupling on saturation loess liquefaction has a feature of segmentation, plastic index plays the main role for loose loess, whereas density is the main control factor to dense loess; Moreover, the influence of density-grain degree coupling on saturated loess liquefaction controlled by cyclic numbers of the vibration, plastic index plays the leading role while the vibration times is small, while the more vibration times, the bigger density and higher strength of liquefaction.

Abstract: The structural property is an important influence factor in loess liquefaction, which contains the interaction between the soil granules. According to study by Gao, the loess could be divided into three types as weak cemented loess, half cemented loess and cemented loess based on the grain composition, the consolidation and the weather conditions of the loess when it formed. In this paper, based on microstructure test and dynamic triaxial test of the loess from the Loess Plateau region, liquefaction properties of structural loess was analyzed. The results show that: (1) the structural strength of loess of weak cementing type, half cementing type and cementing type increases in order, and so does the liquefaction strength, (2) the change mechanism of different structural loess’s dynamic strain during liquefying is different, (3) the change of saturation loess’s pore water pressure during liquefying is related to the type of pore and the structural strength.