On March 28th,2025,a catastrophic earthquake measuring Ms 7.9 struck central Myanmar,resulting in extensive damage to buildings,significant casualties and tremendous economic loss.During a two-week on-site investigation,widespread liquefaction phenomena and the consequent damage to structures and infrastructures were investigated across 16 villages(or districts)within the earthquake affected regions.This examination encompassed hundreds of residential houses,two major bridges,several roads,and underground storage tanks,among others.Reports also detailed the consequences of liquefaction-induced lateral spreading,which led to the demolition of houses and casualties.The field survey of liquefaction revealed that the liquefaction phenomena and the associated damage were extensively distributed along the surface rupture,accompanied by substantial sand ejection and severe impacts on structures.Ground fissures resulting from liquefaction constituted a major cause of structural destruction in buildings.The loss of ground bearing capacity remained another impact of liquefaction on structural damage,resulting in subsidence and tilting of buildings.The cases of liquefaction in the Myanmar earthquake reported herein provided experience and lessons for anti-seismic design aimed at mitigating soil liquefaction risks in the Southeast Asia.Through the analysis of the phenomenon and characteristics of soil liquefaction,the methods and techniques for liquefaction hazard mitigation in China can be further refined and improved.

The traditional equivalent linear method relies solely on the maximum shear strain amplitude to calculate the effective shear strain. This can lead to an overestimation of the effective shear strain and a subsequent underestimation of the response under strong nonlinearity. This study proposes an improved computational framework that incorporates more shear strain time history characteristics. The degree of nonlinearity is quantified by measuring the reduction in modulus ratio. It is proposed that nonlinear effects should be considered when the modulus ratio falls below a specified limit value. A modulus ratio of 0.9 is recommended as the critical limit. This limit value is inherent to the computational method itself and remains independent of soil modulus ratios, damping ratios, and input ground motion characteristics. The shear strain corresponding to this modulus ratio limit value is termed the threshold shear strain. All local peak shear strains that exceed the threshold shear strain contribute to the effective parameter calculation. The effective modulus ratio and the effective damping ratio are obtained through time-weighted averaging of the corresponding ratios associated with each peak strain. Numerical simulations were performed using various seismic response analysis methods, including SHAKE, DYNEQ, SITERESPONSE, DEEPSOIL, and the proposed SOILQUAKE (SQ) method, based on 987 sets of ground motion records from 16 KiK-net sites. The simulation results were systematically compared with the actual observations. The results demonstrate that SQ effectively achieves spectral residuals closest to zero across almost all periods. SQ shows a particularly significant improvement in accuracy under strong seismic excitation (peak ground acceleration, PGA > 0.1 g). Mixed-effects regression analysis confirmed the fixed-effect bias of SQ less than 0.03 for short periods (T < 0.4 s), with SQ outperforming other methods by nearly an order of magnitude. Regarding PGA prediction alone, all methods generally demonstrate considerable accuracy when PGA < 0.1 g. However, when PGA > 0.1 g, only SQ and SR remain reliable. SQ is therefore a reliable tool for engineering applications.

Coral sand, commonly found in offshore and marine engineering, is highly susceptible to seismic threats, with liquefaction being a prominent form of seismic damage. Traditional liquefaction assessment methods for terrestrial soils are not applicable to coral sand sites. To address the lack of coral sand liquefaction data, a coupled analysis combining optimized undrained triaxial cyclic tests on saturated coral sand with shear wave velocity (Vs) measurements is presented and a characterization relationship between shear wave velocity and liquefaction strength for coral sand is proposed. Further, by incorporating engineering experience and considering two key parameters commonly used in Chinese liquefaction assessments—groundwater level and burial depth—a technical process for liquefaction assessment in saturated coral sand layers is established. Comparative analysis with existing methods supports the validity of the proposed approach. The method, which was tested retrospectively on Hawaii’s Kawaihae Harbor following a Mw 6.7 earthquake in 2006, showed results consistent with actual conditions. This approach is expected to improve as more seismic data becomes available, and it may also inform the development of liquefaction assessment methods for broadly graded coral soil sites.

Seismic liquefaction represents a persistent and complex engineering challenge in soil dynamics. Post-earthquake damage investigations have shown that damage to buildings caused by site liquefaction constitutes a significant proportion of all seismic damage. The spectral characteristics of ground motions exert a predominant effect on structural damage, and an important issue that needs to be addressed is accurately describing how these spectral characteristics influence the structural fragility. A simplified six-story reinforced concrete (RC) frame model was established. The ratio of peak ground displacement to peak ground acceleration (referred to as Rd2a) was adopted as an indicator of spectral characteristics of ground motions. The collected ground motions were classified into five groups based on their respective Rd2a values. Using the in-built Incremental Dynamic Analysis (IDA) kit on the OpenSees platform, fragility curves of the simplified RC building were calculated under different Rd2a values to further assess the effect of the ratio of the peak ground displacement to peak ground acceleration on structural fragility. Additionally, 22 real ground motion records from liquefied sites (hereafter referred to as liquefied ground motions) and a same number of records from non-liquefied sites were also analyzed. The results underscore the distinct vulnerability patterns of structures on liquefied ground, revealing that the unique spectral shifts inherent in liquefied motions significantly intensify structural fragility compared to non-liquefied conditions.

On March 28, 2025, a catastrophic M 7.9 earthquake shook central Myanmar, causing extensive damage to buildings, significant casualties, and substantial economic loss, making it one of the most severe natural disasters Myanmar has faced in recent years. During an on-site investigation that lasted two weeks, widely spreading liquefaction phenomena and associated damage to buildings and other facilities were investigated in 16 villages or districts in the seismic zones, involving hundreds of residential houses, two large bridges, underground storage tanks, etc. Ground fissures generated by liquefaction tore apart houses, which contributed to a significant impact on house damage. The loss of ground bearing capacity is another impact of liquefaction with regard to structural damage, causing the subsidence and tilting of houses. Several consequences of liquefaction were identified, such as lateral spreading, which demolishes houses and causes casualties, as well as damage to two large bridges as a result of lateral spreading. The cases of liquefaction following the Myanmar earthquake reported on herein provide data and lessons for future seismic desigs to help prevent such disasters in Southeast Asia. Through analyzing the phenomena and characteristics of soil liquefaction, the methods and techniques for liquefaction hazard mitigation in other countries also can be improved.

Ground-motion frequency characteristics have a significant impact on structural damage. A quantitative description of the impact of ground-motion spectral features on structures is an urgent topic that requires solutions. In this study, the ratio of peak displacement to peak acceleration (R d 2 a ) is used as a representative index of the ground-motion spectral characteristics. The seismic records collected from the Kik-net strong-motion array in Japan are grouped according to their R d 2 a values. By adopting the incremental dynamic analysis method, the seismic fragility curves of a six-story RC frame structure loaded by inputting seismic records with different R d2a values are calculated using the OpenSees platform. The influence of R d 2 a values on the structural fragility is analyzed. Ground-motion records of liquefied sites are collected, and the peak ratios of seismic records at the liquefied sites are analyzed to reveal the differences in the fragility of the six-story RC structures at liquefied and non-liquefied sites. The results of this study are expected to serve as a reference for the evaluation of structural fragility and to understand the effect of ground-motion frequency characteristics on the fragility of RC frame structures.

Seismic site response analysis for deep soil is a big challenge for ground-motion prediction in seismic design and seismic hazard evaluation. One-dimension (1D) seismic site response analysis methods, which are principally adopting equivalent linear theory, are still prevailing tools to analyse seismic soil response. The feasibility of such tools to evaluate deep soil response has not been commonly recognized and usually ignored. To straightforwardly address such issue, 30 strong-motion stations installed on soil layers deeper than 50 m from KiK-net strong-motion seismograph network are selected, and then 1218 seismic data recorded by the stations are collected. 5 widely-used seismic site response analysis programs, i.e., Shake2000 (SHAKE), SoilQuake (SQ), SoilResponse (SR), LSSRLI-1 (LS), and DeepSoil (DP), are used to calculate ground acceleration and corresponding 5

Seismic histories induced by minor earthquakes could improve the sand liquefaction resistance, whereas those induced by strong earthquakes could decrease the sand liquefaction resistance. The action of upward pore fluid seepage on shallow sand deposits during the post-liquefaction process was determined to be one of the mechanisms of these natural phenomena. Based on this background, a series of 1g shaking table tests were carried out to analyze the effects of pore fluid seepage on the sand reliquefaction resistance in subsequent earthquakes. Experimental results showed that the decreasing effects of the seepage history on the sand liquefaction resistance were limited by the input seismic intensities and applied hydraulic gradient (i). Weaker or more extensive seismic motions (cyclic stress ratio, CSR<0.32 or >0.67, respectively) and i values less than 0.5 would not noticeably decrease liquefaction resistance. In the case of inputting successive motions with a medium CSR and i=3.0, the liquefaction resistance of the sand deposits with seepage histories decreased in the first two shakes in comparison with the deposit models without seepage histories. A longer seepage duration correlated to a much lower liquefaction resistance. These results demonstrated that the interaction of the soil layers during reconsolidation should be considered in evaluating the liquefaction risk of the ground.

Assessing the risk of earthquake-induced liquefaction in gravelly soils is a new challenge faced by earthquake prevention and disaster reduction efforts in China's engineering sector.In situ shear wave velocity testing is a universally applicable technical method;however,existing methods are not suitable for China.This study establishes a new method for calculating the liquefaction probability of gravelly soils based on shear wave velocity under the Chinese model,and compared it with the CYY(Cao,Youd and Yuan)method,which is based on the CSR(cyclic stress ratio)theory.The comparative analysis using measured data as well as different probability liquefaction threshold models indicates that the proposed Chinese model for calculating the liquefaction probability of gravelly soils based on shear wave velocity can solve the problem of CYY method unsuitable for China and is more advanced than the CYY method.It overcomes the shortcomings of the CYY method,which struggles to simultaneously consider different burial depths of gravelly soil layers and the effects of varying seismic intensities.Both in the deterministic discrimination with a probability of 0.5 and in the reliability of liquefaction probability calculation under measured data,the method proposed in this paper outperforms the CYY method.The proposed formula in this paper has been adopted in the revised version of the General Rules for Performance-Based Seismic Design of Buildings,serving as a model for China,and can provide guidance and technical support for related specifications and engineering applications.

Microbial-induced calcium carbonate precipitation (MICP) is a promising approach to improve the geotechnical engineering properties of granular soils. MICP has advantages of environment friendliness, low disturbance, low cost, etc. Calcareous sand is a special type of granular soil, and its particles are highly irregular and angular. In this paper. a series of experimental tests were undertaken to investigate the influence of soil particle morphology on the efficiency of the MICP process in calcareous sand. Effects of the concentration of bacteria solution and grouting method were quantified and compared in terms of calcium carbonate (CaCO3) content and unconfined compressive strength (UCS). The results show that fractal dimension of the calcareous sand particle ranges from 1.08 to 1.21. Period of 10–35 h after activation is the logarithmic growth stage of the bacteria. Single-phase grouting is better than two-phase grouting method. The UCS of the MICP-treated calcareous sand specimens is about 300–700 kPa and it has an exponential distribution with the CaCO3 content.

Post-earthquake scientific investigation is considered as one of the pillars supporting earthquake engineering. On the 6th of February, 2023, two deadly strong earthquakes, which magnitudes were Mw7.8 and Mw7.5, respectively, shook Southern-Central Turkiye, caused significantly large casualties and tremendous economy loss. Through on-site field survey, liquefaction phenomena and liquefaction-induced damage to buildings were observed. The observations are: (1) the consequences of soil liquefaction included sandboils, lateral spreading, ground subsidence and ground failure caused by loss of bearing capacity; (2) in two liquefied areas, lateral spreading was investigated and the spreading displacement ranged from several centimeters to meters, resulting in damage or demolishing of buildings; (3) in Golbasi town, many 6 to 10-story buildings significantly subsided and tilted due to liquefaction-induced loss of ground bearing capacity. Buildings subsided by tens of centimeters to 2 3 m, and tilted by several degrees to tens of degrees; (4) ground subsidence of tens of centimeters with respect to adjacent buildings was detected. The liquefaction phenomena were compared with those triggered by the 2008 Wenchuan, China, earthquake which maintained similar in magnitude and focal depth. The findings and lessons learnt will enhance the understanding of liquefaction hazard, challenge the current liquefaction countermeasures, and eventually facilitate to improve liquefaction mitigation techniques.

Geological hazard surveys demonstrate that the history of prior seismic events could affect soil liquefaction resistance under the subsequent earthquakes. The liquefaction of soil with prior seismic history seems not sensitive to the densification after prior reconsolidation. Many attempts of the previous studies have concentrated on the mechanism, impacts, and evaluation of prior destructive seismic history, including large cyclic shear strain and liquefaction history. However, less attention has been paid to the mesoscopic mechanism of the non-liquefying histories commonly caused by weak earthquakes from an experimental view. In this study, centrifuge shaking table tests combined with an inflight mesoscopic image acquisition system were utilized to investigate the macroscopic and mesoscopic behaviors of clean sand deposits under complex seismic sequences. The sequence consisted of three types of seismic motion with different intensities that were equivalent to weak, medium, and strong earthquakes, respectively. Experimental results show multiple weak earthquakes can improve sand liquefaction resistance obviously, which was demonstrated by different evolution patterns of reliquefaction resistance during the tests with and without prior weak earthquakes. The beneficial effects of non-liquefying history were also seen in the cases of models with extensive liquefaction history. Mesoscopic images analysis revealed that multiple weak earthquakes eliminated slender voids, made the particles that constituted loose mesostructures rotate to equalize the voids distribution, and caused quick downward movement of small particles to strengthen interlocking effects among particles.

The sand liquefaction evaluation formulae based on the standard penetration test (SPT) blow count in China's seismic design code are the most widely used and authoritative liquefaction evaluation formula proposed by Chinese scientists, which are suitable for China's national conditions. The basic principle of this formula is to use the groundwater level of the site and the burial depth of the saturated sand layer to correct the reference value of SPT blow count to obtain the critical blow count. The SPT reference blow counts in this formulae depend on liquefaction data. However, the database used to construct the evaluation formulae in the codes mainly comes from post earthquake survey and testing data as well as earthquake damage experience of several earthquakes that occurred in China in the 1960s and 1970s, but the data has not been systematically updated. By adding liquefaction data from recent earthquakes in China, the number of liquefaction data is significantly increased. Drawing on the theoretical framework of liquefaction discrimination methods in China's codes, this paper gives the benchmark values of SPT blow counts under different intensities through data analysis, and constructs a new liquefaction discrimination formula. To verify the formulae, back-judgement on the data were performed, and the results indicate the success rates of the new formulae are fairly satisfactory and keep balance between liquefaction data and non-liquefaction data. The analytical results presented herein can be helpful for revising liquefaction evaluation methods in seismic design codes.

深厚土层地震反应计算是工程抗震以及地震安全性评价工作中的一个难点,基于等效线性化理论的一维土层反应分析方法是当前土层地震反应计算的主流程序,但后者对前者计算结果的可靠性缺少系统的认识.选取日本KiK-net强震观测台网中30个覆盖层厚度大于50 m的台站场地和台站所记录的1 218条地震数据,采用DEEPSOIL(DP)、LSSRLI-1(LS)、SHAKE2000(SHAKE)、SOILQUAKE(SQ)以及 SOILRESPONSE(SR)等 5 款一维土层地震反应分析程序计算场地地表加速度及反应谱.通过标定加速度反应谱的3个特征参数(即峰值加速度(peak ground acceleration,PGA)、特征周期Tg和平台值βmax)的计算值与实测值对比,评估5款土层反应计算程序的可靠性.分析结果表明:5款程序中SR计算PGA的准确率最高,SQ最低;Tg的计算结果各程序间差别不明显,SQ的准确率略高于其他程序;5款程序计算βmax的准确率基本无差别.计算特征参数准确率随着参数相对误差水平的增加而增大.分析结果可为采用等效线性化方法计算深厚土层场地地震反应的可靠性评价提供依据.

能量传递率是衡量贯人类试验锤击效率的一个重要指标.国外对这一指标需要进行现场实测,进而修正贯入试验的锤击数,建立评价场地承载力、液化势等特性的标准化锤击数.国内规范中,则较少考虑贯入试验的锤击能量传递率的问题,且缺少现场试验测试数据,导致基于贯人类试验锤击数的地基评价方法难以与国外标准进行横向对比.为解决这一问题,选取川滇地区西昌地震实验场的3个勘察试验点.采用能量测试仪实测标准贯入试验能量传递率,研究我国常规SPT试验装置锤击效率,并评价其稳定性.试验实测结果显示,现场标准贯入试验的锤击能量传递率均值基本超过75％.能量传递率随着贯入深度的增加稍有增加,地表下20 m范围内增长幅值为10％左右.试验结果可为评价我国常规SPT试验设备的锤击效率提供依据.

地震液化是工程场地在地震中面临的主要威胁,为从液化研究角度探查 2023 年 2 月 6 日土耳其 7.8 级地震局部震害特点,本文借助地理信息系统(geographic information system,GIS)技术,应用宏观液化等级和宏观液化指数的评估方法,通过对此次地震的液化震害调查影像资料分析,阐释了此次地震中场地液化及其震害的主要宏观特征.研究表明:场地液化是此次地震的主要震害之一,除地表破裂外,液化引发不均匀震陷,造成建筑物倾倒;液化激励地震动为 0.15～0.50 g,主要集中于0.25 g以下;按修订的麦卡利烈度(modified mercalli intensity,MMI)表划分,液化点分布于Ⅶ度区,而按我国仪器烈度标准则液化点分布于Ⅶ～Ⅹ度区域;液化宏观指数与以上两种烈度评定方法的关系在趋势上存在较大差异.

Field data from liquefaction case histories are essential for the development, calibration and validation of the liquefaction evaluation methods, and prime standard for the validation of current liquefaction theories. By collecting liquefaction data from Chi-Chi, Bachu and Songyuan earthquakes in China, the volume of data in the Chinese liquefaction database based on the standard penetration test (SPT) is significantly increased from 121 to 465. This database is then used to validate the reliability of four liquefaction evaluation methods based on SPT, i.e. evaluation method suggested in Code for Seismic Design of Buildings (code method for short), two hyperbolic models, and the simplified cyclic stress ratio (CSR) method. The results indicate that the two hyperbolic models can satisfactorily distinguish the liquefaction data from the non-liquefaction data, with success rates higher than 85% for both liquefaction data and non-liquefaction data. The code method and the simplified CSR method exhibit disadvantages for liquefaction evaluation. The predicted results are not satisfactory for all four evaluation methods for seismic intensity of 7, as the liquefaction data are mixed with the non-liquefaction data for this intensity. The overall success rates of the four evaluation methods are high for the data when the seismic intensities are 8 and 9. A new probabilistic liquefaction evaluation equation based on the CSR method is proposed by regression analysis of the new liquefaction data. The predicted liquefaction critical state lines are in reasonable agreement with reported probabilistic equation, even though the number of datasets adopted is different. The Chinese code method has obvious limitation with conservative results for soil layers at the depth greater than 10 m. The analytical results provide reference for improving the liquefaction evaluation method in Chinese code.

作为区域土特征理论研究的起点,以土力学和土动力学经典理论和实际资料为基础,提出了相应的概念、原理、准则和实证.从土的经典本构模型出发,提出了双控制参数的概念,以此作为区域土特征理论的基础.提出了区域土特征函数的概念,阐明了其定义、内涵和外延,提出了包括控制性、普适性、完备性、原位性、一致性、可操作性和存在性等属性要求在内的区域土特征函数构建准则.针对常见的砂土和黏土,提出了采用N-vs特征函数表征其区域土力学和工程特性的思想,给出了构建方法,阐明了其原理,通过 17个国家 77个地区实际N-vs函数关系的分布特征,论证了砂土和黏土N-vs特征函数的存在性.

Displacement spectrum is an essential aspect in displacement-based seismic design (DBSD) philosophy that, comparing to force-based, describes in a more explicit way the structural response and the damage. To better apply DBSD, the displacement spectrum model in period ranging up to 15 s is rephrased using recent high-quality digital strong motion data worldwide, particularly from China territory. After systematical analysis conducted of the influence factors as magnitude, distance, and site conditions on displacement spectrum, it is found that magnitude played a more predominant role in characterizing displacement spectrum that is normalized by peak ground-motion displacement than site conditions and distance. A simplified magnitude-scaled model consisting of four straight line segments constrained by three corner periods and their corresponding amplitudes is proposed to model the normalized displacement spectrum. Comparison with seismic data and the published models verifies the applicability of the proposed model especially for strong earthquakes. Residual analysis indicates the simplified model satisfactorily matches the records with respect to magnitude and distance but the variability of model prediction slightly tends to grow as magnitude and distance increase.