Long Wei Chen

In Situ Test Methods in Bachu-Jiashi Earthquake Liquefied Evaluation

The serious soil liquefaction phenomenon in Bachu-Jiashi earthquake on 24th February, 2003, which is the most prominent phenomena of sand liquefaction since the Tangshan Great Earthquake in 1976. Based on the earthquake liquefied investigation, inspect SPT and CPT applicability in situ tests. The results show that our country SPT specification and CPT specification of non-liquefied sites evaluation rate is higher than liquefied sites evaluation success rate, the liquefied sites evaluation rate are 88% and 88% respectively, but for liquefied sites evaluation rate are 38% and 55%. The result is tends to danger and the reason need further investigation, so establish a suitable liquefied prediction method should be to the future work in the local area.

A Study on the Analysis Method of Soil Layer Seismic Response in Seasonal Frozen Site

The analysis of ground motion on seasonal frozen soil mainly focused on the conventional soil, neglecting the impact of the permafrost which causes the obvious defeats in the existed calculation procedure. In this paper, the author proposed that we should apply the field test of shear wave velocity to the soil layer response calculation, improve the test method of dynamic shear modulus, and adopt the regular analysis method of soil layer response to the calculation of frozen soil site.

Correlation of Site Characteristic Period with Predominant Period of Ground Acceleration by a Simplified Model

Site characteristic period is an important index in seismic zonantion and seismic resistance design. The characteristics of the ground motions are conceptually related with site characteristics. A simplified single-layer model is used for simulating horizontal strata under seismic loading to calibrate the correlation of site characteristic period with the predominant period of ground motion. The analytical results show that the inputted motions were amplified considerably by the site typically for the period components which were close to the site characteristic periods; with the shear wave velocity of the soil layer decreases with respect to the initial shear wave velocity, the predominant period of ground motion increases; the site characteristic periods are consistent with the predominant periods of the ground motion.

Research on Zoning Technology of the Liquefaction Seismic Settlement Based on MAPGIS

Liquefaction seismic settlement is one of the typical nature disasters caused by earthquake, which always leads to wall cracking due to uneven settlement of the building. In the previous research work, scientists only study on the failure mechanism and the calculation method of the seismic settlement, the zoning technology about liquefaction seismic settlement have not been proposed. So that, utilizing the function of MAPGIS, this paper puts forward the zoning technology of the liquefaction seismic settlement.

Study on In Situ Test Based on Survey of Bachu Earthquake

Based on survey of the Bachu-Jiashi earthquake liquefaction sites, much new basic liquefaction information were obtained and China’s liquefaction database was enriched. A detailed investigation of the Bachu earthquake liquefaction site was conducted, in which three kinds of in situ test measures were used to obtain the site information, and given China mainland SPT data of liquefaction site increase by 40%. By site investigation, international standard liquefaction site CPT data were obtained, and also, the first measurement of liquefaction site data by SPT and CPT index was conducted. With the new data, the feasibility of liquefaction discrimination methods of China was inspected.

Liquefaction Macro-Characteristics in Chengdu Region in Wenchuan Ms8.0 Earthquake

In Wenchuan earthquake, liquefaction phenomena and relevant damage in Chengdu region was extensive. Through field investigation, macro-liquefaction characteristics in Chengdu region are outlined, i.e., (1) Liquefaction zones (belts) mainly were located in Dujiangyan city; (2) Liquefaction has been observed in seismic intensities VI, VII, VIII, IX and X, but mainly concentrated in intensities VII and VIII; (3) Heights of liquefaction water-jet mostly ranged in 1m to 3m, and the highest was more than 10m; (4) The ejected materials in liquefied sites covered many soil categories, nearly 67% of fine sand and 11% of gravel; (5) Liquefaction generally caused ground fissures, but obvious ground subsidence were not detected. Although the ejected materials mainly were fine-grained soil, the actual liquefaction was prevalent gravel soil

Frequency Response Characteristic of a Flexible FBG Sensing Beam for Measuring Dynamic Lateral Displacement of Soil in Shaking Table Tests

Flexible fiber Bragg grating (FBG) sensing beams are used to measure dynamic shear response of liquefied soil to ground motions in a shaking table test. Measurement systems typically consisting of bulky arrays of sensor bundles can be instead. But the different frequency response characteristics between the soil and beam generate testing errors. In this work, the sensing beam method is introduced, and the frequency response of the sensing beams will be obtained in an experiment on a shake table.

Simplified Models to Evaluate Site Characteristic Period

Characteristic site period is an important index in seismic zonantion and seismic resistance design. In seismic response spectrum theory, the characteristic design period is closely related with site characteristic site period which is comprehensively covering site parameters (site categories, site shear wave velocity, site thickness, etc.). Two models, i.e., single-layer model and double-layer model, are adopted and theoretical solutions are deduced by means of the amplification coefficient function. The natural site period are theoretically deduced and presented

Liquefaction Features in Mianyang Region in Wenchuan Earthquake

In Wenchuan earthquake, liquefaction and relevant damage in Mianyang region were significant and of the three major regions, but the liquefaction phenomena were clearly different from Chengdu and Deyang regions. Through field investigation and engineering geological data analysis, this paper studies the liquefaction features and distribution in Mianyang area. Analysis shows that: (1) Liquefaction zones (belts) mainly were located in Youxian area of Mianyang city, Jiangyou city and Weicheng-Dongxuan town area; (2) Liquefaction has been observed in regions of intensities VII and VIII, but mainly concentrated in intensity VII; (3) Heights of water-jet were about one meter with the highest 3-4m; (4) The ejected materials in liquefied sites basically covered kinds of soil types, i.e., nearly 80% of fine sand followed by 11% of gravel; (5) Liquefied zones were associated with cracks, resulting in farmland, houses, a railway station, schools and factories damage in different extents. Jiangyou railway station is the most typical example of gravelly soil liquefaction. (6) The liquefied soil in Mianyang region is mixed, e.g., liquefied layers were gravel layers in Jiangyou city; sandy layer liquefied in Youxian area of Miangyang city; and the liquefied soil was probable gravel or sand in Weicheng-Dongxuan town area but the gravel liquefaction possibility was high

Comparison of Blind Detection of Liquefaction by Suzuki and SY Methods

To mitigate liquefaction hazard, real-time liquefaction monitoring technique is investigated. And the reverse liquefaction detection method from seismic records is the key point. The existing methods are limited and the reliability requires test. In 2011, an earthquake of magnitude 6.3 struck in New Zealands South Island. Serious liquefaction phenomena were reported, which provides an opportunity to verify the existing liquefaction detection methods. Twenty-seven acceleration records within 50km to the epicenter are selected to perform a blind detection for existing two methods, including Suzuki and Sun-Yuan method. The blind detection results indicate that Sun-Yuan method obtains correct results for three known liquefied sites, and both method are correct for a reported non-liquefied site. The number of identically detected results is 22 by two methods. The identified results will be verified by actual observation for the 23 sites excluding 4 confirmed sites.