Ground response analysis of Kanpur soil along Indo-Gangetic Plains

The present work deals with 1D and 2D ground response analysis and liquefaction analysis of alluvial soil deposits from Kanpur region along Indo-Gangetic plains. Standard penetration tests and seismic down hole tests have been conducted at four locations namely IITK, Nankari village, Mandhana and Bithoor at 1.5 m interval up to a depth of 30 m below the ground surface to find the variation of penetration blows and the shear wave velocity along the depth. From the selected sites undisturbed as well as representative soil samples have been collected for detailed soil classification. The soil profiles from four sites have been considered for 1D and 2D ground response analysis by applying the free field motions of three Himalayan earthquakes namely Chamba earthquake (M_w—5.1), Chamoli earthquake (M_w—6.4) and Uttarkashi earthquake (M_w—6.5). An average value of Peak Ground Acceleration (PGA) obtained from 1D and 2D analysis is considered for liquefaction analysis and post-liquefaction settlement. The excess pore water pressure ratio is greater than 0.8 at a depth of 24 m from ground surface for IITK, Nankari village, Bithoor sites. More than 50% of post liquefaction settlement is contributed by layers from 21–30 m for all sites. In general, the soil deposits in Kanpur region have silty sand and sand deposits and are prone to liquefaction hazards due to drastic decrease of cyclic resistance ratio (CRR) at four chosen sites in Kanpur.     

Liquefaction assessments using seismic piezocone penetration (SCPTU) test investigations in Tangshan region in China

Shear wave velocity (V_s) measurements from seismic piezocone penetration (SCPTU) soundings have been increasingly used for site characterization and liquefaction potential assessments. Several sites in Tangshan region, China liquefied during the Tangshan earthquake, M_w=7.8 in 1976 and these sites were characterized recently using the SCPTU device. Other sites in the same region where liquefaction was not observed are also included in the present field investigations. Three liquefaction assessment models-based on measured shear wave velocity, shear modulus and tip resistance parameters of SCPTU are evaluated in this paper for their accurate predictions of liquefaction or non-liquefaction at the test sites. Analyses showed that the shear wave velocity—liquefaction resistance model with normalized overburden vertical stress have yielded a success rate of 78% in predicting liquefied site cases and another similar approach with mean stress based normalization has a success rate of 67%. The correlation of q_c/G_o-CRR_7.5 based on geological age has correctly assessed the liquefaction potential at most sites considered in this research. Overall, all three models based on shear wave velocity, shear modulus and cone tip resistance are proven valuable in the assessments of liquefaction at the present test sites in the Tangshan region.     

Analysis of the liquefaction phenomena in the village of Vittorito (L��Aquila)

This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila earthquake (moment magnitude M_w = 6.3), approximately 45 km far from the epicentre. In the document, first, an estimation of the seismic motion in the area has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave velocity V_s and horizontal stress index K_D. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the area, produced by the L’Aquila earthquake, was very low.     

GIS-based soil liquefaction susceptibility map of Mumbai city for earthquake events

The problem of liquefaction of soil during seismic event is one of the important topics in the field of Geotechnical Earthquake Engineering. Liquefaction of soil is generally occurs in loose cohesionless saturated soil when pore water pressure increases suddenly due to induced ground motion and shear strength of soil decreases to zero and leading the structure situated above to undergo a large settlement, or failure. The failures took place due to liquefaction induced soil movement spread over few square km area continuously. Hence this is a problem where spatial variation involves and to represent this spatial variation Geographic Information System (GIS) is very useful in decision making about the area subjected to liquefaction. In this paper, GIS software GRAM++ is used to prepare soil liquefaction susceptibility map for entire Mumbai city in India by marking three zones viz. critically liquefiable soil, moderately liquefiable soil and non liquefiable soil. Extensive field borehole test data for groundwater depth, standard penetration test (SPT) blow counts, dry density, wet density and specific gravity, etc. have been collected from different parts of Mumbai. Simplified procedure of Youd et al. (2001) is used for calculation of factor of safety against soil liquefaction potential. Mumbai city and suburban area are formed by reclaiming lands around seven islands since 1865 till current date and still it is progressing in the area such as Navi Mumbai and beyond Borivali to Mira road suburban area. The factors of safety against soil liquefaction were determined for earthquake moment magnitude ranging from M_w = 5.0 to 7.5. It is found that the areas like Borivali, Malad, Dahisar, Bhandup may prone to liquefaction for earthquake moment magnitude ranging from M_w = 5.0 to 7.5. The liquefaction susceptibility maps were created by using GRAM++ by showing the areas where the factor of safety against the soil liquefaction is less than one. Proposed liquefaction susceptibility map of Mumbai city can be used by researchers for earthquake hazard analysis, for the preventive measures in disaster management, for urban planning and further development of Mumbai city and suburban area.     

Characterization of liquefaction resistance in gravelly soil: large hammer penetration test and shear wave velocity approach

Gravelly soil is generally recognized to have no liquefaction potential. However, liquefaction cases were reported in central Taiwan in the 1999 Chi-Chi Taiwan earthquake and in the 1988 Armenia earthquake. Thus, further studies on the liquefaction potential of gravelly soil are warranted. Because large particles can impede the penetration of both standard penetration test and cone penetration test, shear wave velocity-based correlations and large hammer penetration tests (LPT) are employed to evaluate the liquefaction resistance of gravelly soils. A liquefied gravelly deposit site during the Chi-Chi earthquake was selected for this research. In situ physical properties of soil deposits were collected from exploratory trenches. Instrumented LPT and shear wave velocity (V_s) measurements were performed to evaluate the liquefaction resistance. In addition, large-scale cyclic triaxial tests on remolded gravelly soil samples (15 cm in diameter, 30 cm in height) were conducted to verify and improve LPT-based and V_s-based correlations. The results show that the LPT and shear wave velocity methods are reasonably suitable for liquefaction assessment of gravelly soils.     

Comparison of SPT and <Emphasis Type="Italic">V</Emphasis><Subscript>s</Subscript>-based liquefaction analyses: a case study in Erciş (Van,Turkey)

Liquefaction which is one of the most destructive ground deformations occurs during an earthquake in saturated or partially saturated silty and sandy soils, which may cause serious damages such as settlement and tilting of structures due to shear strength loss of soils. Standard (SPT) and cone (CPT) penetration tests as well as the shear wave velocity (V _s)-based methods are commonly used for the determination of liquefaction potential. In this research, it was aimed to compare the SPT and V _s-based liquefaction analysis methods by generating different earthquake scenarios. Accordingly, the Erci? residential area, which was mostly affected by the 2011 Van earthquake (M _w = 7.1), was chosen as the model site. Erci? (Van, Turkey) and its surroundings settle on an alluvial plain which consists of silty and sandy layers with shallow groundwater level. Moreover, Çald?ran, Erci?–Kocap?nar and Van Fault Zones are the major seismic sources of the region which have a significant potential of producing large magnitude earthquakes. After liquefaction assessments, the liquefaction potential in the western part of the region and in the coastal regions nearby the Lake Van is found to be higher than the other locations. Thus, it can be stated that the soil tightness and groundwater level dominantly control the liquefaction potential. In addition, the lateral spreading and sand boiling spots observed after the 23rd October 2011 Van earthquake overlap the scenario boundaries predicted in this study. Eventually, the use of V _s-based liquefaction analysis in collaboration with the SPT results is quite advantageous to assess the rate of liquefaction in a specific area.     

Threshold seismic energy and liquefaction distance limit during the 2008 Wenchuan earthquake

Estimating the possible region of liquefaction occurrence during a strong earthquake is highly valuable for economy loss estimation, reconnaissance efforts and site investigations after the event. This study identified and compiled a large amount of liquefaction case histories from the 2008 Wenchuan earthquake, China, to investigate the relationship between the attenuation of seismic wave energy and liquefaction distance limit during this earthquake. Firstly, we introduced the concept of energy absorption ratio, which is defined as the absorbed energy of soil divided by the imparted energy of seismic waves at a given site, and the relationship between the energy absorption ratio and the material damping ratio was established based on shear stress–strain loop of soil element and the seismic wave propagation process from the source to the site. Secondly, the threshold imparted seismic energy of liquefaction was obtained based on existing researches of absorbed energy required to trigger liquefaction of sandy soils and the ground motion attenuation characteristics of the 2008 Wenchuan earthquake, and the liquefaction distance limit of this earthquake was estimated according to the proposed magnitude–energy–distance relationship. Finally, the field liquefaction database of 209 sites of the 2008 Wenchuan earthquake was used to validate such an estimation, and the field observed threshold imparted seismic energy to cause liquefaction in recent major earthquakes worldwide was back-analyzed to check the predictability of the present method, and several possible mechanisms were discussed to explain the discrepancy between the field observations and the theoretical predictions. This study indicates that seismic energy attenuation and liquefaction distance limit are regional specific and earthquake dependent, and 382 J/m³ is the average level of threshold imparted seismic energy to cause liquefaction for loose saturated sandy soils, and the corresponding liquefaction distance limit is approximately 87.4 km in fault distance for a M_w?=?7.9 event in the Chengdu Plain. The proposed regional energy attenuation model and threshold imparted seismic energy may be considered as an approximate tool in evaluating the liquefaction hazard during potential earthquakes in this area.     

Evaluation of temperature and freeze–thaw effects on excess pore pressure generation of fine-grained soils

The November 3, 2002 Denali-Alaska earthquake (M_w=7.9) caused significant liquefaction associated damage to various infrastructure built on fine-grained soils. The seismic response, liquefaction potential, and excess pore pressure generation of soils in cold regions, especially those of fine-grained nature, have not been studied thoroughly and therefore are not well-understood. This paper presents results from an extensive laboratory study on the characteristics of excess pore pressure generation and liquefaction potential of fine-grained soils. Laboratory-constituted soils specimens were tested in four categories: (1) tests on specimens subjected to no thermal conditioning or freeze–thaw cycles; (2) tests on specimens conditioned at 24, 5, 1, 0.5, and −0.2 °C; (3) tests on specimens subjected to 1–4 freeze–thaw cycles; and (4) tests on specimens conditioned at near-freezing temperatures of 0.5 and −0.2 °C through different freeze–thaw paths. Strain-controlled, undrained, cyclic triaxial tests were performed at shear strain levels of 0.005–0.8%. Specimens conditioned at different temperatures were found to generate significantly different pore pressures with cyclic loading. The excess pore pressure generation at near or slightly below freezing was found to change dramatically. A transitional change in the dynamic soil behavior, attributed to unfrozen- or frozen-dominant pore water, was discovered. The threshold shear strain was also found to be influenced by the temperature. Subjecting the soil specimens to 1, 2 and 4 freeze–thaw cycles caused a reduction in excess pore pressure generation and slight change in the threshold shear strain. The temperature conditioning path to reach the target temperature was found to be important on the development of excess pore pressure at near and slightly below-freezing temperatures.     

Predicting seismic liquefaction potential of sands by optimum seeking method

The feasibility of using the optimum seeking method to assess the seismic liquefaction potential of sands has been investigated. Optimization theory is a very important branch of applied mathematics and has a wide application in the practical world. Using the available field sand liquefaction data, the influence of various factors is quantified using the optimum seeking method. The factors considered are: the earthquake magnitude M, the distance of the site from the source of the earthquake L, the depth of the water table D_w, the depth of the sand deposit D_s, and the standard penetration test (SPT) blow count N. The most important factors have been identified as the earthquake magnitude and the SPT blow count. Prediction results show that the proposed method is effective and feasible. Since neither normalization of the SPT blow count nor calculation of the seismic shear-stress ratio are required, the proposed method is simpler and more direct than the conventional methods of evaluating liquefaction potential.     

饱和黄土场地原位试验及液化势评价

目前,主要依靠室内动力试验对黄土液化势进行评价。由于黄土特殊的结构性,室内试验对其饱和的过程较为复杂,且与实际场地饱和黄土差异明显,导致室内黄土液化试验结果并不能代表现场饱和黄土的抗液化强度。本文选取兰州市西固区寺儿沟村某饱和黄土场地进行钻孔测试,现场实施了标准贯入试验、静力触探试验以及剪切波速测试。应用Robertson的土类指数分类图对该场地不同含水率黄土的土类进行了界定,确定了饱和黄土属于类砂土,有液化势。应用NCEER推荐方法,计算了3组原位试验数据的饱和黄土循环抗力比（CRR）,通过与1976年唐山地震和1999年集集地震液化土CRR对比,得出了饱和黄土抗液化强度很低的结论。     

Liquefaction potential and strain dependent dynamic properties of Kasai River sand

The availability of efficient numerical techniques and high speed computation facilities for carrying out the nonlinear dynamic analysis of soil-structure interaction problems and the analysis of ground response due to earthquake loading increase the demand for proper estimation of dynamic properties of soil at small strain as well as at large strain levels. Accurate evaluation of strain dependent dynamic properties of soil such as shear modulus and damping characteristics along with the liquefaction potential are the most important criteria for the assessments of geotechnical problems involving dynamic loading. In this paper the results of resonant column tests and undrained cyclic triaxial tests are presented for Kasai River sand. A new correlation for dynamic shear damping (D_s) and maximum dynamic shear modulus (G_max) are proposed for the sand at small strain. The proposed relationships and the observed experimental data match quite well. The proposed relationships are also compared with the published relationships for other sands. The liquefaction potential of the sand is estimated at different relative densities and the damping characteristics at large strain level is also reported. An attempt has been made to correlate the G_max with the cyclic strength of the soil and also with the deviator stress (at 1% strain) from static triaxial tests.     

A surface seismic approach to liquefaction

The liquefaction potential of soils is traditionally assessed through geotechnical approaches based on the calculation of the cyclical stress ratio (CSR) induced by the expected earthquake and the ‘resistance’ provided by the soil, which is quantified through standard penetration (SPT), cone penetration (CPT), or similar tests. In more recent years, attempts to assess the liquefaction potential have also been made through measurement of shear wave velocity (V_S) in boreholes or from the surface. The latter approach has the advantage of being non-invasive and low cost and of surveying lines rather than single points. However, the resolution of seismic surface techniques is lower than that of borehole techniques and it is still debated whether it is sufficient to assess the liquefaction potential.In this paper we focus our attention on surface seismic techniques (specifically the popular passive and active seismic techniques based on the correlation of surface waves such as ReMi^TM, MASW, ESAC, SSAP, etc.) and explore their performance in assessing the liquefaction susceptibility of soils. The experimental dataset is provided by the two main seismic events of M_L=5.9 and 5.8 (M_W=6.1, M_W=6.0) that struck the Emilia-Romagna region (Northern Italy) on May 20 and 29, 2012, after which extensive liquefaction phenomena were documented in an area of 1200 km².The CPT and drillings available in the area allow us to classify the soils into four classes: A) shallow liquefied sandy soils, B) shallow non-liquefied sandy soils, C) deep non-liquefied sandy soils, and D) clayey–silty soils, and to determine that on average class A soils presented a higher sand content at the depth of 5–8 m compared to class B soils, where sand was dominant in the upper 5 m. Surface wave active–passive surveys were performed at 84 sites, and it was found that they were capable of discriminating among only three soil classes, since class A and B soils showed exactly the same V_S distribution, and it is possible to show both experimentally and theoretically that they appear not to have sufficient resolution to address the seismic liquefaction issue.As a last step, we applied the state-of-the art CSR–V_S method to assess the liquefaction potential of sandy deposits and we found that it failed in the studied area. This might be due to the insufficient resolution of the surface wave methods in assessing the Vs of thin layers and to the fact that Vs scales with the square root of the shear modulus, which implies an intrinsic lower sensitivity of Vs to the shear resistance of the soil compared to parameters traditionally measured with the penetration tests. However, it also emerged that the pure observation of the surface wave dispersion curves at their simplest level (i.e. in the frequency domain, with no inversion) is still potentially informative and can be used to identify the sites where more detailed surveys to assess the liquefaction potential are recommended.     

Non-linear site response simulations in Chang-Hwa region during the 1999 Chi–Chi earthquake, Taiwan

The destructive 1999 Chi–Chi earthquake (M_w 7.5) was the largest inland earthquake in Taiwan in the 20th century. Several observations witness the non-linear seismic soil response in sediments during the earthquake. In fact, large settlements as well as evidence of liquefaction attested by sand boils and unusual wet ground surface were observed at some sites. In this paper, we present a seismic response simulation performed with CyberQuake software on a site located within the Chang-Hwa Coastal Industrial Park during the 1999 Chi–Chi earthquake in Taiwan. A non-linear multi-kinematic dynamic constitutive model is implemented in the software. Computed NS, EW and UP ground accelerations obtained with this model under undrained and two-phase assumptions, are in good agreement with the corresponding accelerations recorded at seismic station TCU117, either for peak location, amplitudes or frequency content. In these simulations, liquefaction occurs between depths 1.3 and 11.3 m, which correspond to the observed range attested by in place penetration tests and other liquefaction analyses. Moreover, the computed shear wave velocity profile is very close to post-earthquake shear wave velocity profile derived from correlations with CPT and SPT data. Finally, it is shown that in non-linear computations, even though a 1D geometry is considered, it is necessary to take into account the three components of the input motion.     

Liquefaction of soil in the Tokyo Bay area from the 2011 Tohoku (Japan) earthquake

Immediately following the 11th March 2011 M_w 9.0 Tohoku (Japan) earthquake, a field investigation was carried out around the Tokyo Bay area. This paper provides first-hand observations (before or just at the onset of repair) of widespread liquefaction and the associated effects. Observations related to uplift of manholes, settlement of ground, performance of buildings and bridges and the effects of ground improvements are also presented. Recorded ground motions near the Tokyo Bay area were analysed to understand their key characteristics (large amplitude and long duration). Lessons learnt are also presented.     

Gravity variation before Kunlun mountain pass western <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript>=8.1 earthquake

The relation between the gravity variation features and M _S=8.1 earthquake in Qinghai-Xizang monitoring area is analyzed preliminarily, by using spatial dynamic variation results of regional gravity field from absolute gravity and relative gravity observation in 1998 and 2000. The results show that: 1) M _S=8.1 earthquake in Kulun mountain pass western occurred in the gravity variation high gradient near gravity’s high negative variation; 2) The main tectonic deformation and energy accumulation before M _S=8.1 earthquake are distributed at south side of the epicenter; 3) The range of gravity’s high negative variation at east of the M _S=8.1 earthquake epicenter relatively coincides with that rupture region according to field geology investigation; 4) Gravity variation distribution in high negative value region is just consistent with the second shear strain’s high value region of strain field obtained from GPS observation.     

The aftermath of 2011 Van earthquakes: evaluation of strong motion, geotechnical and structural issues

October 23rd, 2011 M _L 6.7 (M _w 7.2 KOERI) Tabanli-Van Earthquake caused damage in a widespread area specifically in the settlement regions throughout the Lake Van. A number of 58 buildings totally collapsed during the shake with 52 of them however, reported to be in Ercis district. 17 days after this destructive event, another earthquake of M _L 5.6 hit the region again on the 9th of November having the epicentral location at Edremit district. The second earthquake mostly affected the central region of Van province with a number of 25 totally collapsed buildings and furthermore it significantly increased the existing structural damages. Strong motion records from both earthquakes and their impacts on structures as well as geotechnical issues are studied in this paper. Extensive liquefaction triggered lateral spread, landslide and slope failure cases were observed mainly at non-residential areas. Soil amplification is evaluated to be one of the main reasons for the heavy damage occurred in Ercis. Furthermore, site investigations and damage assessment performed after each earthquake proved that the observed damages are strongly correlated with insufficient qualities of structural materials, inadequate detailing and poor workmanship.     

基于GNSS资料分析漾濞MS6.4地震前应变时空演变特征

基于云南省内及邻区2009—2020年GNSS观测数据解算结果,在各个测点时间序列和速度场的基础上,采用克里金插值方法估计区域应变率场;以连续基准站时间序列为约束,获取漾濞M_S6.4地震近场区域的块体应变时间序列。分析发现:漾濞地震发生在前期最大剪应变高值区以及面应变高梯度带的张压转换区,发震的时间处于区域应变积累速率逐渐降低的过程之后。震中近场区域均以NW向断层的右旋走滑应变积累为主,且大多呈现持续增强趋势,与漾濞地震的发震断层走向及其破裂特征一致。震前震区东部块体出现了短期应变趋势转折及反向加速的异常现象,反映了应力-应变积累在接近临界破裂状态时的非线性调整。     

Assessing CPT-based methods for liquefaction evaluation with emphasis on the cases from the Chi-Chi, Taiwan, earthquake

In the early morning (1:47 Taiwan time) of September 21, 1999, the largest earthquake of the century in Taiwan (M_w=7.6, M_L=7.3) struck this island country. The earthquake killed more than 2400 people and caused great destruction to buildings, bridges, dams, highways, and railways. One of the causes for heavy damages to the structures is soil liquefaction and ground settlement during the earthquake. In this paper, investigation of soil liquefaction and case histories of liquefaction are presented. Three CPT-based simplified methods, the Robertson method, the Olsen method, and the Juang method, are examined using the case histories derived from the Chi-Chi earthquake. The results of the comparison show that the Juang method is more accurate than the two methods in predicting liquefaction potential of soils based on the cases derived from the Chi-Chi earthquake, although all three methods are quite comparable in accuracy.     

Undrained behaviour of two silica sands and practical implications for modelling SSI in liquefiable soils

The aim of the present study is twofold. Firstly, the paper investigates the undrained cyclic and post-cyclic behaviour of two silica sands by means of multi-stage cyclic triaxial tests. Secondly, based on the post-cyclic response observed in the element test, the authors formulate a simplified stress–strain relationship that can be conveniently used for the construction of p–y curves for liquefiable soils. The multi-stage loading condition consists of an initial cyclic loading applied to cause liquefaction, followed by undrained monotonic loading that aimed to investigate the post-cyclic response of the liquefied sample. It was found that due to the tendency of the liquefied soil to dilate upon undrained shearing, the post-liquefaction strain–stress response was characterised by a distinct strain–hardening behaviour. The latter is idealized by means of a bi-linear stress–strain model, which can be conveniently formulated in terms of three parameters, i.e.: (i) take-off shear strain, γ_to, i.e. shear strain required to mobilize 1 kPa of shear strength; (b) initial secant shear modulus, G₁, defined as 1/γ_to; (c) post-liquefied shear modulus at large strain, G₂ (γ⪢γ_to). Based on the experimental results, it is concluded that these parameters are strongly influenced by the initial relative density of the sample, whereby γ_to decreases with increasing relative density. Differently both shear moduli (G₁ and G₂) increases with increasing relative density. Lastly, the construction of new p–y curves for liquefiable soils based on the idealized bi-linear model is described.     

A Review of the Calculation Formula for the Four-component Borehole Strainmeter and Application to Earthquake Cases

Based on the principle formula for the four-component strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several four-component borehole strainmeters near the epicenter of the Yiliang M_S5.7 earthquake in 2012 and the Ludian M_S6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake.