Weakness and mechanical anisotropy of phyllosilicate-rich cataclasites developed after mylonites of a low-angle normal fault (Simplon Line,Western Alps)

The Simplon Fault Zone is a late-collisional low-angle normal fault (LANF) of the Western Alps. The hanging wall shows evidence of brittle deformation only, while the footwall is characterized by a c. 1 km-thick shear zone (the Simplon Fault Zone), which continuously evolved, during exhumation and cooling, from amphibolite facies conditions to brittle-cataclastic deformations. Due to progressive localization of the active section of the shear zone, the thermal-rheological evolution of the footwall resulted in a layered structure, with higher temperature mylonites preserved at the periphery of the shear zone, and cataclasites occurring at the core (indicated as the Simplon Line). In order to investigate the weakness of the Simplon Line, we studied the evolution of brittle/cataclastic fault rocks, from nucleation to the most mature ones. Cataclasites are superposed on greenschist facies mylonites, and their nucleation can be studied at the periphery of the brittle fault zone. This is characterized by fractures, micro-faults and foliated ultracataclasite seams that develop along the mylonitic SCC′ fabric, exploiting the weak phases mainly represented by muscovite and chlorite. Approaching the fault core, both the thickness and frequency of cataclasite horizons increase, and, as their thickness increases, they become less and less foliated. The fault core itself is represented by a thicker non-foliated cataclasite horizon. No Andersonian faults or fractures can be found in the footwall damage zone and core zone, whilst they are present in the hanging wall and in the footwall further from the fault. Applying a stress model based on slip tendency, we have been able to calculate that the friction coefficient of the Simplon Line cataclasites was <0.25, hence this fault zone is absolutely weak. In contrast with other fault zones, the weakening effect of fluids was of secondary importance, since they accessed the fault zone only after an interconnected fracture network developed exploiting the cataclasite network.     

ON THE CHARACTERISTICS OF NON-LINEAR SOIL RESPONSE AND DYNAMIC SOIL PROPERTIES USING VERTICAL ARRAY DATA IN JAPAN

Non-linear response of the soil is investigated by comparing the spectral ratios (uphole/downhole) using weak and strong motions. Data from seven vertical arrays in Japan are analysed in this study. The frequency-dependent transfer function of soil is calculated as a ratio of the spectrum at uphole to the spectrum at downhole, considering the horizontal component of shear wave. In spectral ratio analysis auto- and cross-spectra are employed. The reduction in the predominant frequency of the transfer function with increases in excitation level reflects the non-linear response of the soil. Results of analysis demonstrate a significant non-linear ground response at six sites with surface PGA exceeding 90 gal. However, the results of one site show the linear response up to 130 gal surface PGA. Furthermore, the in situ strain-dependent soil behaviour is examined through the shear modulus – shear strain relationship. When compared, the actual and laboratory results of the shear strain – shear modulus relationship are in agreement. Additionally, a good consistency between the tendency of reduction in shear modulus ratio with shear strain increases, and reduction of predominant frequency with ground motion increases, confirms the significance of non-linearity in site effects study.     

奇异性理论在弱异常信息提取中的应用—以冀北隐伏中-酸性侵入岩体为例

冀北地区是河北省矿产资源重要聚集地之一,成矿条件优越,其中中-酸性侵入岩体与银铅锌多金属矿床成矿密切相关。然而,大量的第四系覆盖压制了一些深部及隐伏弱异常成矿信息,使得常规化探方法在该覆盖区提取效果微弱。本文运用奇异性分析及主成分分析对冀北1：20万水系沉积物常量元素化探数据进行分析处理,提取区内成矿元素弱异常,并将其与未进行奇异性处理的结果进行对比。结合区域地质背景、物化探资料圈定覆盖区内与中-酸性侵入岩体有关的异常区,对成矿作用、成矿规律进行分析、讨论,以期揭示区内元素富集规律。结果显示,上述组合方法可以有效提取元素弱异常并进行成矿有利区圈定,并且圈定位置与已知岩体位置、区域构造条件相吻合,共圈出隐伏异常点7个,推测其为成矿远景区。     

环保型弱凝胶护壁护心钻井液研究与应用

海域浅层气地质调查和盐湖环境科学钻探在松散砂岩钻探取样工程中,存在孔壁易坍塌、成孔率低等技术难题,为此开展了松散砂岩地层环保型弱凝胶护壁护心钻井液技术研究。通过弱凝胶结构研究及成胶剂、交联剂及抗盐降滤失剂等材料优选,研发了一套环保型弱凝胶护壁护心钻井液,评价了钻井液的流变性、滤失性、抑制性、护心性能、环保性能等性能,并在山西某盐湖环境科学钻探工程进行现场应用。室内及现场应用结果表明：研制的弱凝胶护壁护心钻井液具有良好的流变性、降滤失性、抑制性（岩屑回收率96.3%）、护壁护心性能及环保性能（BOD5/COD比值24.6%,EC50值47950 mg/L）,能有效解决松散砂岩类地层孔壁坍塌、岩屑不易携带等问题,在松散地层钻探工程中具有广阔的应用前景。     

基于新型探测资料对西安一次弱降水预报失误的原因分析

利用微波辐射计、激光测风雷达、多普勒雷达、相控阵雷达等新型探测资料、地面加密观测资料、ERA5再分析及多模式数值预报结果对2022年4月24日西安城区一次弱降水预报出现明显失误的原因进行分析,结果表明：(1)全球数值预报模式和中尺度数值预报模式对本次过程西安城区均报有明显降水,主要原因为模式对低层相对湿度预报明显偏大;(2)多种新型探测数据分析认为近地层湿度条件较差及中层的绝对水汽含量低,中层的干暖空气不利于成云致雨,垂直上升运动不强,且由于低层非常干燥,使水滴在下沉过程中蒸发,从而无法形成雨滴下落,这些原因共同造成西安城区无降水,低层相对湿度预报偏大是造成这次西安城区降水预报失误的主要原因之一;(3)造成西安城区近地层湿度条件差的原因是城市干热岛效应和低层干暖平流输送,且降水云团翻越秦岭后其湿空气绝热下沉至城区后出现增温降湿,使得城区形成较为深厚的干层,即使有雨滴在下落过程中也会造成更强的蒸发,这也是城区没有降水的重要原因之一;(4)预报员主观预报订正出现空报主要是源于对边界层水汽、抬升条件等关键降水要素缺乏订正能力,且对大城市的干热岛效应和秦岭山区地形影响研究不足。     

基于直线感知增强的边缘提取算法

根据视觉识别边缘的感知特性,提出了一种基于直线感知增强的弱边缘的边缘提取算法。借鉴视觉的直线感知方式,针对弱边缘整体上呈直线分布的特点将其筛选出来,进行编组、连接和扩展。与Edison边缘提取算子的比较实验证明,本算法在对弱边缘的提取和虚假边缘的抑制上有显著增强。     

弱流场调制下的海面微波散射模拟研究

根据海面微波散射的多尺度模型以及波流相互作用理论,对一维弱流场调制下的海面微波散射截面进行了数值模拟。结果表明,利用数值方法直接求解波作用量方程获得的海浪调制谱并结合多尺度模型可以较好地模拟弱流场引起的雷达散射截面的变化。内波等海洋现象调制了海浪谱,使得雷达散射截面反映出这些海洋特征,整个调制过程的模拟对于分析这些海洋现象并更好地利用其雷达数据具有重要意义。     

粉煤灰碎石混凝土灌注桩法加固软弱地基效果的分析与检验

对由深厚软弱土层组成的地基,采用粉煤灰碎石混凝土灌注桩法予以加固处理时,其施工机具相对简单,工期短,节约“三材”,投资省,具有显著的经济效益。由粉煤灰碎石混凝土灌注桩和深厚软弱土层共同构成的复合地基的工程特性,介于一般碎石桩复合地基与混凝土桩桩基之间,其基本特征是:承载力的提高,主要是置于深厚软弱土层中的粉煤灰碎石混凝土灌注桩的排水和垂直加筋作用的结果;其承载机理,部分具有一般碎石桩复合地基的特征;在结构物荷载作用下,其桩、土荷载分担特征,比较接近于普通混凝土桩桩基。     

金沙江地震带强震动及其与现今弱震活动关系

包括川滇菱块及马边－大关，宣威－弥勒地区在内的金沙江地震带记载（录）了川滇两省发生的绝大部分中、强以上地震，为我国西南一主要地震区。本文重点研究了该范围内强震的重复性及现今弱震密集区的强震危险性问题。金沙江地震带强震具有很高的原地重复性，７级以上强震原地重复率达６５．４％，平均复发时间１５７年；６级地震原地重复率达４１．８％，平均复发时间为２７．２年。川滇地区现今弱震活动密集区在活动期内本身发生６级以上强震的可能性很小。四川地区大多数情况下强震发生在距密集区４０－５０千米处，云南情况较复杂。但在作今后较长时间危险性分析预测时，现今弱震密集区本身仍有发生６级地震的危险，虽然发生７级以上地震可能性不大。     

安太堡露天煤矿排土场基底黄土的微结构演化与弱层的形成机理

本文根据安太堡露天煤矿排土场基底黄土的粘土矿物组成的微结构及其在分级荷载下微结构变化的研究，论述了排土场基底黄土内弱层的形成机理，提出弱层是在上覆排土压力下由于黄土的微结构变化而形成的演化弱层。并指出弱层的形成是导致排土场失稳滑坡的主要控制因素，这种弱层在新排土场设计时期并不存在，极具隐蔽性，但在设计时必须考虑在排土增至一定高度后，弱层的形成对排土场稳定性的影响，否则必将会存在重大滑坡隐患。