高速黄土滑坡的一种机理——饱和黄土蠕动液化

本文提出了高速黄土滑坡的一种机理——饱和黄土蠕动液化。文中列举了甘肃地区饱和黄土蠕动液化造成高速滑坡的实例,并从饱和黄土受力前后的应力条件及土体结构内部强度的变化分析了饱和黄土液化的机理。通过现场及室内试验得出剪切强度、剪切速度、饱和度及其它影响因素对液化程度的重要影响。提出了饱和黄土蠕、滑动液化导致高速滑坡的过程。最后,还讨论了高速滑坡及泥流的速度问题。     

Analysis of ground motions at Treasure Island site during the 1989 Loma Prieta earthquake

Site response analyses and coherence studies were conducted at the Treasure Island site where surface motions were recorded during the Loma Prieta earthquake. The analyses were conducted using a nonlinear dynamic effective stress method which took into account the effects of the liquefaction that occured at the site. The rock motions recorded at nearby Yerba Buena Island were used as input motions. Computed and recorded ground motions transverse to the direction of wave propagation and associated response spectra were in good agreement. Agreement was also good in the radial direction, except in certain frequency bands higher than 1·25 Hz. Coherence studies showed that some of these discrepancies may be due to low coherence between the Treasure Island and Yerba Buena motions in these same frequency bands.     

球体内点位错产生的球型位移场：Ⅰ．理论

本文研究了ＳＮＲＥＩ模型内点位错产生的球型位移场．讨论了在用源函数表示的点力作用下的非奇次平衡方程的积分方法．通过定义位错Ｌｏｖｅ数，讨论了４种独立的位错解，并由此描述３种基本位错问题，即剪切位错、引张位错和爆破．导出了这３种位错产生的位移场的计算公式，可以用来计算任意位错源在任意点处的位移场．     

打入桩对液化饱和亚砂土改善的探索──无排地下孔隙水措施的处理实例

本文目的是探索饱和亚砂土层在不排水条件下,沉桩后,抗液化能力的改善效果。文章对土壤中粘粒含量,颗粒的级配,井点降水和打桩程序作了分析。结论是:适当的级配和规定打桩程序,土壤的抗液化能力就能有很明显的改善。     

高层建筑液化地基处理的研究

本文主要介绍拟建于严重液化场区内高层建筑地基处理的研究成果。研究表明:采用袋装砂井处理,能够收到防液化效果,但应注意时间效应;当地震烈度为7°时,对桩基础的高层建筑,只需利用沉桩作用,即可获得较好的抗震加固效果;若袋装砂井与沉桩共同作用进行处理,其抗震加固效果尤为理想,即使当地震烈度达到8°时,也不会产生液化现象。     

3种钻孔应变仪记录的玛多MS7.4地震同震响应特征对比分析

针对2021年5月22日青海玛多MS7.4地震,采用3种型号的钻孔应变仪观测到的应变资料对比分析同震应变波,结果表明3种仪器记录同震的初动时间、波动幅度和持续时间等存在一定差别:在震中距相当的情况下,TJ型体应变仪和RZB型四分量钻孔应变仪存在波动幅度变化小、持续时间短的问题,难以从背景变化中区分同震响应,影响钻孔仪器同震规律研究; YRY?4型四分量钻孔应变仪波动幅度变化大,持续时间长,在映震效果上表现较为突出。     

土动力学研究综述及思考

随着国家重大构筑物的不断建设实施,考虑土体具有较高的动力易损性和致灾特性,工程构筑物的工程地质灾害和岩土工程动力致灾特性研究需要愈显迫切。通过对当前土动力学与岩土地震工程方面研究进展进行归纳总结,着重从土的动力强度、土的动本构关系、砂土的振动液化、铁路路基中的动应力、边坡地震永久变形和稳定性、挡土墙上的地震土压力等六个方面进行叙述,对其中涉及的各种研究方法进行比较和论述,最后提出了土动力学有待进一步深入研究的若干问题和未来发展方向,以期基于土动力学的发展而提升构筑物的抗震设防水平。     

Les différents mécanismes à l’origine de la diversité des séismites,leur identification dans le Pliocène du Saïss de Fès et de Meknès (Maroc) et leur signification tectonique

Résumé

Des structures synsédimentaires de type dish-structure, plis disharmoniques, figures de charge, dislocation et des destructions du litage et intrusions sableuses, observées dans le Saïss, sont interprétées comme des structures induites par une liquéfaction sismique de sables marins et fluviátiles, parfois associée à des injections sableuses. La place de ces structures parmi les divers types de séismites est discutée par rapport à l’influence des caractéristiques de granulométrie, de diagenèse et de pente qui conditionnent les différents modes de déformation. Les deux niveaux déformés marocains sont replacés dans le déroulement de la tectonique pliocène au sud du Rif. © Elsevier, Paris     

Indicative Structures of Paleoseismicity in the Acequion River Valley,San Juan Province,Central-Western Argentina

Evidence for paleo-seismicity has been discovered in the Acequión river valley, in West central Argentina. Two Holocene rock avalanches have been observed; the most recent of these dammed a lake, whose sediments contain liquefaction structures. At least five paleo-earthquakes affected this region during the late Quaternary, as deduced from the succession of their secondary effects. The magnitude and the probable tectonic source of these paleo-events are discussed. The observed liquefaction features associated with slumps, joints, fractures, and faults, should be generated by M>5 earthquakes related to the nearby quaternary Cerro Salinas fault, which belongs to the Eastern Precordillera fault system. These data extend the regional seismicity record to the Holocene and highlight the high seismic hazard in this part of Argentina.     

CPT-based probabilistic evaluation of seismic soil liquefaction potential using multi-gene genetic programming

In this paper, liquefaction potential of soil is evaluated within a probabilistic framework based on the post-liquefaction cone penetration test (CPT) data using an evolutionary artificial intelligence technique, multi-gene genetic programming (MGGP). Based on the developed limit state function using MGGP, a relationship is given between probability of liquefaction (P_L) and factor of safety against liquefaction using Bayesian theory. This Bayesian mapping function is further used to develop a P_L-based design chart for evaluation of liquefaction potential of soil. Using an independent database of 200 cases, the efficacy of the present MGGP-based probabilistic method is compared with that of the available probabilistic methods based on artificial neural network (ANN) and statistical methods. The proposed method is found to be more efficient in terms of rate of successful prediction of liquefaction and non-liquefaction cases, in three different ranges of P_L values compared to ANN and statistical methods.