Surface crack evolution patterns in freeze-thaw damage of fissured rock bodies

To explore the effects of freeze‒thaw cycles on the mechanical properties and crack evolution of fissured sandstone,biaxial compression experiments were carried out on sandstone subjected to freeze‒thaw cycles to characterize the changes in the physical and mechanical properties of fissured sandstone caused by freeze‒thaw cycles.The crack evolution and crack change process on the surface of the fissured sandstone were recorded and analysed in detail via digital image technology(DIC).Numerical simulation was used to reveal the expansion process and damage mode of fine-scale cracks under the action of freeze‒thaw cycles,and the simulation results were compared and analysed with the experimental data to verify the reliability of the numerical model.The results show that the mass loss,porosity,peak stress and elastic modulus all increase with increasing number of freeze‒thaw cycles.With an increase in the number of freeze‒thaw cycles,a substantial change in displacement occurs around the prefabricated cracks,and a stress concentration appears at the crack tip.As new cracks continue to sprout at the tips of the prefabricated cracks until the microcracks gradually penetrate into the main cracks,the displacement cloud becomes obviously discontinuous,and the contours of the displacement field in the crack fracture damage area simply intersect with the prefabricated cracks to form an obvious fracture.The damage patterns of the fractured sandstone after freeze‒thaw cycles clearly differ,forming a symmetrical"L"-shaped damage pattern at zero freeze‒thaw cycles,a symmetrical"V"-shaped damage pattern at 10 freeze‒thaw cycles,and a"V"-shaped damage pattern at 20 freeze‒thaw cycles.After 20 freeze‒thaw cycles,a"V"-shaped destruction pattern and"L"-shaped destruction pattern are formed;after 30 freeze‒thaw cycles,an"N"-shaped destruction pattern is formed.This shows that the failure mode of fractured sandstone gradually becomes more complicated with an increasing number of freeze‒thaw cycles.The effects of freeze‒thaw cycles on the direction and rate of crack propagation are revealed through a temperature‒load coupled model,which provides an important reference for an in-depth understanding of the freeze‒thaw failure mechanisms of fractured rock masses.

Sandbox Modeling of the Fault-increment Pattern in Extensional Basins

Three series of sandbox modeling experiments were performed to study the fault-increment pattern in extensional basins. Experimental results showed that the tectonic action mode of boundaries and the shape of major boundary faults control the formation and evolution of faults in extensional basins. In the process of extensional deformation, the increase in the number and length of faults was episodic, and every ＇episode＇ experienced three periods, strain-accumulation period, quick fault-increment period and strain-adjustment period. The more complex the shape of the boundary fault, the higher the strain increment each ＇episode＇ experienced. Different extensional modes resulted in different fault-increment patterns. The horizontal detachment extensional mode has the ＇linear＇ style of fault-increment pattern, while the extensional mode controlled by a listric fault has the ＇stepwise＇ style of fault-increment pattern, and the extensional mode controlled by a ramp-flat boundary fault has the ＇stepwise-linear＇ style of fault-increment pattern. These fault-increment patterns given above could provide a theoretical method of fault interpretation and fracture prediction in extensional basins.

裂陷盆地构造演化及盆地伸展模式——以东濮凹陷为例

东濮凹陷是我国东部典型的裂陷盆地。盆地的构造演化经历了早古生代至三叠纪的克拉通盆地旋回和新生代的裂陷盆地旋回。新生代裂陷盆地旋回又划分为早期裂陷、强烈裂陷、晚期裂陷和晚第三纪整体坳陷4个阶段。东濮凹陷基底伸展量的变化总趋势是由北向南加大,地壳上部的伸展构造变形为简单剪切伸展模式,而地壳下部具有纯剪切机制。滑脱面变异带可能是造成东濮凹陷内桑村集-桥口-白庙横向构造变换带、南北构造活动差异性以及油气富集程度差异性的重要原因。

南秦岭晚古生代伸展构造特征及意义

采用构造岩石地层—沉积盆地—热水成矿流体及沉积组合—构造变形分析等方法 ,对秦岭造山带晚古生代伸展构造特征及意义进行了系统研究。结果表明 :秦岭造山带从加里东期末—海西期末一直处于 (剪切 )伸展体制下 ,形成一系列伸展构造 ,其伸展构造样式主要有同生断裂、剥离断层、陆表海域中的盆 -岛构造、地堑 -地垒式盆地构造、三级热水沉积成矿盆地 ,叠合沉积盆地内的伸展构造样式有褶叠层、分层剪切流变构造、滑塌同沉积构造、阶梯状同生断层等 ;这些伸展构造样式显示秦岭微板块是以伸展作用发生陆壳变形的 ,可称为秦岭型伸展构造样式 ;伸展构造是主要控矿构造 ,低序次同生断裂是含矿热水运移的通道 ,三级热水沉积成矿盆地是聚矿空间和热水沉积成矿场所 ,热水喷溢通道口及含矿热水沉积岩相是矿层赋存的部位。认为秦岭型伸展构造样式对研究区域成矿学和区内的矿产资源勘查与预测有重要的理论和应用价值。

黄骅坳陷中区大型斜向变换带及其油气勘探意义

依据断层产状、断裂组合和盆地构造样式分析结果,在黄骅坳陷中区识别了一个大型斜向变换带。该变换带主要发育于古近纪,沿走向表现为不同幅度的同沉积背斜,延伸距离达70km。变换带由两组倾向相反的正断层叠覆形成,其东西两侧分属两个伸展构造体系。以西呈半地堑构造样式,以东则呈地堑构造样式。变换带的位置与黄骅—聊城—兰考大型走滑断裂带北延段一致,并发育有典型的花状构造,表明基底结构的差异以及深部走滑断裂长期活动是其产生的内在原因。斜向变换带古近系储集砂体丰富,并发育有上超尖灭和断背斜两种有利圈闭类型,是研究区一个重要的油气聚集带。

渤海地区新构造格局

根据新近系—第四系盖层断裂发育的最新资料,按成因将渤海地区新构造期断裂分为继承活动断裂和新生断裂两种类型;依走向又可分成北东—北东东、北西、北东(偏北)、近东西和北北东向5组,其中继承活动的北西向北京—蓬莱断裂带和北东(偏北)向营口—潍坊断裂带北段,以及新生的北东向庙西北—黄河口断裂带是区内主干构造。在新构造应力场中,庙西北—黄河口和北京—蓬莱断裂带是一对共轭活动的构造带,营口—潍坊断裂带北段为右旋逆平移活动断裂带。这3条活动断裂带将渤海地区分成渤东南、渤西南、渤西北和渤东北4个活动块体,展现出新的构造格局,而与古近纪伸展拉分的盆地构造格局明显有异。其原因是构造发育的动力条件和应力状态发生了显著变化。新构造格局在很大程度上控制和影响了渤海地区的油气成藏和地震活动。

东胜断块系与东胜式铅锌矿床

辽东早元古宙拗拉槽中的铅锌矿床,可划分为层状矿床和脉状矿床两大类。本文论述了后一种类型的典型代表——东胜式铅锌矿床的控矿因素和矿床特征。依据大量地质事实,作者认为:东胜式铅锌矿床的控矿构造是与基底花岗岩活动密切相关的中生代半地堑系;矿质来源于地壳深部液态矿源层;中生代岩浆活动是矿液上升的热动力。综合这三大因素,建立了东胜式矿床的成矿模式。由此,期望对进一步找矿能有一定的指导意义。

琼东南—珠江口盆地深水区构造样式及其分布特征

南海区域构造运动复杂,对其北部深水区的构造样式及分类标准尚缺乏全面、系统的研究。为此,以该区琼东南—珠江口盆地为重点研究对象,基于区域地震反射资料,结合盆地的结构特征,分析、总结了深水区构造样式和分布特征。结果表明:①根据构造样式形成的动力学机制,可以将琼东南—珠江口盆地深水区划分为伸展构造样式、走滑构造样式与重力构造样式3类;②伸展构造样式可继续划分为地堑式、平面式半地堑、铲式半地堑及坡坪式半地堑;走滑构造样式主要表现为剖面上的花状构造、平面上的雁列断层及马尾状断层等;重力构造样式表现形式多样,既有以侧向滑动为主要特征的滚动背斜、重力滑动断层,也有以垂向运动为主的垮塌构造、底辟构造;③上述3类构造样式分布于盆地的3个构造层中,与盆地演化过程中所表现出的动力学机制密切相关。伸展构造主要分布于盆地的下构造层(裂陷期盆地);走滑构造分布于中下构造层(裂陷期盆地—裂陷后坳陷期盆地);重力构造样式分布广泛,在盆地深层—浅层均有分布,但表现形式不同。这些成果与认识对该区后续勘探开发具有十分重要的意义。

塔河地区断裂构造样式及其演化

塔河地区受区域动力背景和塔里木盆地构造演化制约,在震旦纪以来的地质演化历史中受多期次多方向构造应力场控制,经历了多个伸展、挤压、走滑(扭动)等构造旋回。深入分析了塔河地区不同的断裂构造类型和分布,揭示其断裂演化规律。认为塔河地区发育有伸展、挤压、走滑三大构造样式,具体可细分为地堑式、地垒式、断阶式、单断式和“Y”字形或反“Y”字形、平板式逆冲、铲式逆冲、反铲式逆冲、叠瓦状逆冲、逆冲滑脱、背冲、对冲、平行扭动、聚敛扭动和离散扭动,断裂构造的空间分布具有明显的分区、分层、分段差异性。分析结果为下一步油气勘探提供理论依据。

珠三坳陷阳江凹陷构造特征及其对油气成藏的影响

在对研究区地震资料精细解释的基础上,对原阳江凹陷及其南缘低凸起重新进行了构造单元划分。阳江低凸起北支将原阳江凹陷分隔为阳江东、西两个凹陷,阳江东凹陷可以进一步分为东1洼和东2洼。阳江北断裂是阳江东、西两个凹陷主要的控凹断裂,根据断裂走向拐点和阳江东、西凹陷的分界可以把阳江北断裂划分为3段,分别是西段、中段和东段,西段控制阳江西凹陷,中段控制东1洼,东段控制东2洼。断裂各段活动规律不同,其中断裂中段控制的东1洼的主要活动期在晚始新世和早渐新世,控制文昌组和恩平组的湖相沉积,勘探潜力最好。继承、叠加发育的伸展构造样式是阳江东、西两凹陷的主要构造样式,断层型圈闭和披覆背斜型圈闭是该地区发育的主要圈闭类型。勘探实践表明,垂向运移和近源成藏是阳江东、西两凹陷主要的成藏规律。

Structure prediction for error pattern and extension of Welch-Berlekamp theorem

As the Welch-Berlekamp (W-B) theorem accurately predicts structure of error locator polynomials of the error patterns, it results in the Welch-Berlekamp algorithm of decoding cyclic codes. However, it is only valid within the BCH bound. Now, a prediction formula for error locator determination is presented based on the study of theory of minimal homogeneous interpolation problem, which extends the Welch-Berlekamp theorem and expands the Welch-Berlekamp algorithm so that the constraint from the BCH

营口地区辽河群盖县岩组的构造样式

盖县岩组是解决辽河群构造样式的重要层位。通过对盖县岩组内构造样式的解析，发现它与其它岩组一样，于吕梁运动期间经历了三幕构造运动。第一幕发生于拉伸作用阶段，形成了独特的早期伸展构造组合；第二、三幕发生于收缩阶段，其中第二幕构造线走向为ＮＥ，褶皱样式总貌为“两背叁向”，第三幕构造运动形成了本区的大构造格局，构造线走向为ＮＷ～ＮＷＷ。在研究区内，三幕构造叠加明显，尤其是后两幕褶皱叠加，于区内西南部表现为穹隆状—新月形—蘑菇状型式，而区内北东部表现为穹隆—盆地叠加型式。文中对其它构造形迹亦作了阐述。

福建大田建爱地区多金属矿的构造特征及其成矿意义

通过对研究区区域构造发展史的概述和斑岩型、似层状多金属矿的构造特征论述，试图说明斑岩型、似层状热液型多金属矿受燕山晚期造山带伸展构造的控制， 并提出了成矿的构造模式。

Alluvial sedimentation and tectonostratigraphic evolution in a narrow extensional zigzag basin margin (northern Teruel Basin, Spain)

The northern part of the eastern margin of the extensional Neogene Teruel Basin(central-eastern Spain)consists of a non-linear,zigzag fault zone made of alternating ca.2 km long,NNW-SSE trending segments and shorter NNESSW ones.Good outcrop conditions made possible a comprehensive integrated stratigraphic and structural study,especially focused on coarse clastic sediments deposited along the basin margin.Well-exposed stratal relationships with boundary faults,allowed the analysis of tectonic influence on sedimentation.Synsedimentary deformation includes growth faulting,rollover anticlines,and monoclines and associated onlap stratal terminations,angular unconformities,and other complex growth strata geometries.One of them is the onlap-over-rollover bed arrangement described here for the first time,which reveals the competition between tectonic subsidence and sedimentary supply.Both,the structural inheritance(dense Mesozoic fracture grid)and the dominant,nearly‘multidirectional’(σ1 vertical,σ2≈σ3),Pliocene extensional regime withσ3 close to E-W,are considered to have controlled the margin structure and evolution.Tectono-stratigraphic evolution includes:(i)reactivation of inherited NNW-SSE faults and development of W-SW-directed small alluvial fans(SAF)while NNE-SSW segments acted as gentle relay ramp zones;(ii)progressive activation of NNE-SSW faults and development of NW-directed very small alluvial fans(VSAF);during stages i and ii sediments were trapped close to the margin,avoiding widespread progradation;(iii)linking of NNW-SSE and NNE-SSW structural segments,overall basin sinking and widespread alluvial progradation;(iv)fault activity attenuation and alluvial retrogradation.The particular structure and kinematic evolution of this margin controlled alluvial system patterns.Size of alluvial fans,directly set up at the border faults,was conditioned by the narrowness of the margin,small catchment areas,and proximity between faults,which prevented the development of large alluvial fans.The size of the relay zones,only a few hundred meters wide,acted in the same way,avoiding them to act as large sediment transfer areas and large alluvial fans to be established.These features make the Teruel Basin margin different to widely described extensional margins models.

基于可拓分析的信息模式识别方法

采用可拓评判方法,应用物元概念和关联函数,确定了玉米螟种群动态分级识别的的经典域物元和节域物元,提出了一种新的基于可拓分析的信息模式识别方法,并探讨了其应用.应用结果表明,历史拟合率达100%,1995、1996两年预报,其结果与实际一致.说明该识别方法具有良好的应用前景,一种全新的模式识别分类器.

The discovery of the Neoarchean mafic dyke swarm in Hengshan and reinterpretation of the previous “Wutai greenstone belt”

The structural mapping and section study indicate that the “greenstone belts” in the southern to central parts of Hengshan were intensively sheared and transposed mafic dyke swarm, which originally intruded into the Neoarchean grey gneiss and high-pressure granulite terrain (HPGT). The HPGT is characterized by flat-dipping structures, to the south it became steep and was cut by the Dianmen mafic dyke swarm. After high-pressure granulite-facies metamorphic event, the mafic dyke swarm occurred, and was associated with the extensional setting and reworked by the late strike-slip shearing. The zircon age dating proves that the Dianmen mafic dyke swarm was emplaced during the period between 2499±4 Ma and 2512±3 Ma, followed by late tectonothermal reworking. The Dianmen mafic dyke swarm further documents the extensional episode in the central to northern parts of North China Craton (NCC), providing the important constraint for the limit between Archean and Proterozoic and correlation between NCC and other cratonic blocks of the world.