Xiao Ming Yuan

Experimental Study of Liquefaction Resistant Characteristics of Remodeled Clayey Sands

Cyclic triaxial tests were carried out for remodeled saturated clayey sands with the clay content varying in a relatively wide range from 0% to 40%. In the tests, saturated uniformity clayey sands were obtained by pre-freezing method, i.e. immersing samples in pure water for 12 hours under vacuum, and then, freezing the sample to -15°C for 6 hours. Experimental results indicate that the lowest liquefaction resistance in mixtures occurs when clay contents is of the order of 15%. The ratio of liquefaction shear stresses of the specimens obtained using pre-freezing method are larger than those obtained with the traditional deposit-in-water method.

The Preliminary Study on the Impact of the Velocity Situ Test Standard Deviation to the Response Spectra in Deep-Soft Sites

The test results of shear-wave velocity in engineering are of being importance increasingly, but the the uncertainty of the wave test result has influenced the seismic design throughout. In order to describe this uncertainty accurately , the paper has taken some research on the deep-soft sites seismic response. By using SHAKE 2000 program and entering various types of ground motions, the authors discussed the effect of shear-wave velocity standard deviation of several velocity values in deep-soft site to the ground response spectra and PGA(Peak Ground Acceleration). The results are as followed: the standard deviation of the shear-wave velocities has almost no influence on the acceleration response spectra and the PGA of the site; the varieties of response spectra and PGA under different intensity of earthquake can be nearly ignored. With the increasing number of the shear-wave velocity data, results of the study would be further in-depth and perfection.

Analysis on the Bias of Seismic Ground Motion Prediction in a Shallow Stiff-Soil Site by LSSRL-1 Program

The main causes of the ground motion blind prediction bias are the variability of the adopted program, the shear-wave velocity of the site, and the soil nonlinear dynamic parameters. By considering the variability of shear-wave velocity and the dynamic parameters, this essay used LSSRLI-1 Codes and Mw6.0 seismic record of Parkfield earthquake to calculate ground responses of 9 different conditions at Turkey Flat site. The authors believe that the variability of shear-wave velocity caused the dominant impact to the blind prediction of this shallow stiff-soil site. That impact is much greater than that of the dynamic parameters. LSSRLI-1 program may either underestimate the ground response of the shallow stiff-soil site or may overestimate it, so we should combine the specific site conditions and a large amounts of data to do the further analysis.

Verification of the Applicability of Seismic Safety Evaluation Program LSSRLI-1 in Stiff and Half-Stiff Sites Using Exact Solution

The equivalent linearization program LSSRLI-1, proposed by Xiaojun Li in 1989, is the important content in seismic zoning work and seismic safety evaluation of engineering sites. It is necessary to check the applicability of LSSRLI-1 to all kinds of sites. The mainly elaboration of this paper is verifying the applicability of seismic safety evaluation program LSSRLI-1 in stiff and half-stiff sites by exact solution. The results show that, it is well for both of them in most of the case, which is useful for the engineering practice.

Comparisons of Two Methods for Regional Dividing Technology of Liquefaction Based on ArcGIS

Quantitative characterization of liquefaction degree in the south region of Tangshan city has been done by methods of code evaluation and multi-factor regression evaluation. By use of those criterition, liquefaction degree maps were prpared through collecting totally 65 boreholes, and compiling drilling graphics database and attribute database on ArcGIS. In this procedure, the potential of liquefaction values were given respectively. While the quality and quantity of geotechnical test data directly affact the statistical accuracy with which area can be characterized, different method affact it more considerable. According to these drilling data, liquefaction condition for each borehole was discriminated, and the liquefaction condition of the unknown area was speculated by Kriging interpolation method, then the liquefaction zoning map of south of Tangshan and its southern region is presented based on ArcGIS, and comparisons have been made for the two methods.

Research on Regional Dividing Technology for Liquefaction Based on ArcGIS

To assess liquefaction degree in the south region of Tangshan city, totally 65 boreholes are collected and the establishment of drilling graphics database and attribute database are completed on ArcGIS.Then the potential of liquefaction values are given by a multi-factor regression method, seven factors and four factors for different precisions respectively. According to these drilling data, liquefaction condition for each borehole is discriminated, and the liquefaction condition of the unknown area is speculated by Kriging interpolation method, then the liquefaction zoning map of south of Tangshan and its southern region is presented based on ArcGIS.

The Amplification Effect of Soft Site Based on Records from Borehole Arrays

Data recorded by borehole arrays with sensors installed at surface and geologic layers provide critical information for studies of local site amplification effects. The stations of KiK-net strong-motion seismograph network contain detailed information about the condition of site soil, we can judge the site categories according to these information. The stations have collected a large number of seismic records since operated. These seismic records can be downloaded free from the website of KiK-net if you are the register of the website. This paper select 30 sites-type III and 9 sites-type IV from KiK-net strong-motion seismograph network according to the China code for seismic design of buildings (GB50011-2010), and calculate Amplification Coefficient and Site Coefficient by seismic records from the selected stations. Using above information, this paper give their probability distribution and mean value.

Comparative Analysis on Liquefaction Macro-Characteristics of the Three Major Regions in Wenchuan Earthquake

Through the liquefaction-induced damage of Wenchuan earthquake investigation analysis, this paper studies that the liquefaction features and distribution of the three major liquefied regions in Wenchuan earthquake and the earthquake liquefied damage characteristics are preliminarily comparatively analyzed. The analytical results show that: Mianyang region, Deyang region and Chengdu region are the three major liquefaction affected regions in Wenchuan earthquake. Deyang region is the most serious liquefied region, Chengdu region is the second, and Mianyang region is the lightest. Liquefaction damage was considerably large, and basically was farmland. Liquefied sites mainly concentrated in intensities VIII in Deyang region, the categories of sand ejecta were abundant, and the percentage of gravel ejecta is largest in the three major liquefied regions. Liquefied sites mainly located in intensities VII in Chengdu region, and the sand ejecta covered many sand categories, including fine (silty) sand, medium sand, coarse sand and gravely sand. The liquefaction and relevant damage of Mianyang region were the lightest in the three major liquefied regions, and liquefied sites mainly located in intensities VII. 80% of the sand ejecta were fine-silty sand while coarse sand ejection was not found.

Effect of Loading Amplitude on Soil Deformation under Irregular Waves and Fixed-Number Waves

Through series of dynamic triaxial tests, the relationships of soil deformations under irregular seismic loading and fixed-number constant amplitude loading are analyzed. The effect of loading amplitudes on the relationships is presented. The results shows: (1) soil deformation under irregular seismic loading obviously differs from that under constant amplitude sinusoidal loading, and the strain history is mainly controlled by the performance of ground motion; (2) if 20 cycles of constant amplitude loading is employed instead of irregular seismic loading to correct residual deformation under real seismic loading, loading amplitudes have no effect on soil deformation under irregular waves and fix-number waves.

Theoretical Solution to the Change of Site Predominant Period Caused by Soil Softening

The site predominant period should be changed because of soil softening, which is an important parameter to reflect the dynamic characteristics of the site. In this paper, in order to acquire the theoretical solution to the site predominant period, the actual horizontal site has been simplified into two-particle system. And the influence that caused by the thickness and location of the weak layer on the site predominant period, has been analyzed.