岩石变形破裂过程中电荷感应信号的检测

设计了采用非接触方式、高放大倍数、高效率的电荷传感器,并给出了电荷传感器的设计原理和技术指标。利用研制的电荷传感器对岩石变形破裂过程中产生的电荷感应信号进行了检测试验。结果表明,岩石在变形破裂过程中会产生电荷感应信号,并能够被研制的电荷传感器检测到;电荷感应信号是瞬时脉冲的;随着加载应力水平的增加,电荷感应信号强度增强,在峰值应力前,电荷感应信号强度达到最大值;在破裂面接收到的电荷感应信号较强,主破裂面接收到的信号最强,因而电荷的产生和岩石的破裂有很大的关系。作为正在探索的检测岩石破坏过程的手段之一,电荷感应方法应是一种很具潜力的方法,值得深入研究。     

岩石受压破裂的ULF和LF电磁前兆信号

实验观测到了4类岩性、18块样品在单轴压力下直至破裂发生全过程中的ULF和LF电磁前兆信号。这些不同频率的信号是零散出现的，其形态为一组组脉冲，宽度为4ms～16ms，幅度为0．1mV～1．4mV。实验发现具同一谐振频率的天线收到的信号频次与其相对于裂缝的位置和方位有关。结果还表明，电磁前兆信号的频度与岩样强度有关，抗压强度高的岩样电磁前兆信号多。微破裂可能产生了偶电层，在破裂过程中向外辐射，产生了LF频段的磁信号，ULF磁信号则主要由压磁效应产生。     

岩石破裂过程中电磁辐射的实验研究

在单轴压力下对灰岩、花岗岩、石英岩三种样品的破裂过程与电磁辐射进行了实验室试验。结果表明,含有石英晶体的岩石,在破裂过程中产生的电磁信息,其振幅具有脉冲形态;随着应力水平的增高,电磁脉冲的频度增加,与声发射具有同步发展的趋势;不同结构的介质,主破裂前又呈现出平静和高潮两种不同类型。此外,含有石英晶体的岩石其主破裂及解体过程中,伴随最强的电磁脉冲,出现明显的闪光现象。文中对实验结果作了初步的讨论。     

岩石破裂过程中电磁辐射的实验研究

在单轴压力下对灰岩、花岗岩、石英岩三种样品的破裂过程与电磁辐射进行了实验室试验。结果表明,含有石英晶体的岩石,在破裂过程中产生的电磁信息,其振幅具有脉冲形态;随着应力水平的增高,电磁脉冲的频度增加,与声发射具有同步发展的趋势;不同结构的介质,主破裂前又呈现出平静和高潮两种不同类型。此外,含有石英晶体的岩石其主破裂及解体过程中,伴随最强的电磁脉冲,出现明显的闪光现象。文中对实验结果作了初步的讨论。     

地震序列类型的岩石破裂实验研究

采用花岗岩和砂岩拼合的岩样，做单面直接剪切破坏实验，并以微破裂信息存储分析系统连续采集信号。通过波形图研究发现，诸如“前破-主破-余破型”、“主破-余破型”、“群破型”、“双破或多破型”、“孤立型破裂”等都有波形记录，而大破裂前的“平静”、“密集”、“低频扰动”及“慢破裂”现象也有波形显示。这些结果与天然地震很相似。几乎所有天然地震的类型和震兆异常都能在声发射破裂实验中得到发现和验证。实验还显示，在低应力阶段破裂类型较单一，但随着应力升高和逼近主（大）破裂，破裂类型越来越多，而且低频成分变多的破裂增多，慢破裂也增多。     

岩石失稳破裂前激发极化效应的初步研究

本文介绍了在压应力作用下观测岩石失稳破裂前激发极化效应的实验方法和主要结果。重点研究了沉积砂岩、矿化灰岩和部分橄榄岩的激发极化特征及其变化规律,讨论了岩石的脆柔性质与破裂前兆的关系。实验结果表明:(1)在压应力作用下,岩石的激发极化效应十分明显,规律性强,变化幅度大;(2)随着压应力的增大,极化率出现以下降为主的有规律性的变化,其幅度可达百分之几到百分之几十;(3)普遍记录到了岩石失稳破裂前的极化率前兆特征——加速下降和急剧上升,其变化形态与岩石的脆柔性质有关。最后,本文对岩石激发极化压应力效应的机理及其在地震预报研究中的应用作了初步探讨。     

岩石破裂电磁辐射的频率特性

本文提出岩石破裂时产生的低频电磁辐射起源于微破裂引起的电子发射,并用电四极子模型计算了近区电磁场的频率特性．结果表明,近区电磁场的频率与样品尺寸和初始裂纹长度有关,利用典型实验样品尺寸和花岗岩初始裂纹数据计算出近区电磁场的频率为５０ｋＨＺ－１ＭＨｚ量级．它与已有实验测量结果相符．     

岩石破裂电磁辐射的频率特性

本文提出岩石破裂时产生的低频电磁辐射起源于微破裂引起的电子发射，并用电四极子模型计算了近区电磁场的频率特性．结果表明，近区电磁场的频率与样品尺寸和初始裂纹长度有关，利用典型实验样品尺寸和花岗岩初始裂纹数据计算出近区电磁场的频率为５０ｋＨＺ－１ＭＨｚ量级．它与已有实验测量结果相符．     

Rock fragment distributions and regolith evolution in the Ouachita Mountains,Arkansas, USA

Rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls, erosion, deposition, bioturbation, and weathering. The distribution of rock fragments in regoliths of the Ouachita Mountains, Arkansas, shows that sandstone fragments are common in all layers, even if sandstone is absent in parent material. Shale and sandstone fragments are produced at the bedrock weathering front, but the shale weathers rapidly and intact fragments are rare in the solum. Sandstone is weathered from ridgetop outcrops and transported downslope. Some of these fragments are moved downward, by faunalturbation and by transport into pits associated with rotting tree stumps. Upward movement by treethrow is common, resulting in a net concentration of rocks near the surface. However, the highest fragment concentrations are in the lower regolith, indicating active production at the weathering front. The regolith is a dynamic feature, reflecting the influences of vertical and horizontal processes, of active weathering at the bedrock interface, and of surficial sediment movements. The role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities, and that forest soils have likely been extensively mixed within Holocene and historic time. Copyright © 2005 John Wiley & Sons, Ltd.     

Downstream evolution of wastewater treatment plant nutrient signals using high-temporal monitoring

Wastewater treatment plants are major point-sources of nutrients to streams globally, but the impact on receiving streams is not always clear. Previous research has shown mixed responses in receiving streams, with some showing no net retention through in-stream processing for large distances below plants and some showing high rates of processing and retention. This study focuses on Sandy Run, a small, suburban stream in Montgomery County, PA, that receives effluent from two plants, where effluent makes up an estimated 50% of outlet discharge at baseflow. Two sites were monitored in late summer baseflow using high-temporal loggers to evaluate nitrate and phosphate retention with distance below the plants. Effluent quantity was monitored immediately below the effluent outfalls using specific conductivity as a conservative signal of solute fluctuations throughout the day. A site 1 km downstream showed diel nitrate changes, but despite moderate gross primary productivity and ecosystem respiration rates, there was little net retention of nutrients and the diel nitrate signal can be attributed to advection and dispersion of variable upstream effluent. A site 5.4 km below the plant showed a diel nitrate signal as well, but baseflow daily hysteresis plots of nitrate and specific conductivity showed the effluent and nitrate peaks did not coincide. Instead, the effluent input signal was seen overnight, but there was in-stream removal and release processes during the day. Over the distance to this site, the stream was metabolizing some of the high nutrient loads, although gross primary productivity and ecosystem respiration rates were lower. It is important to understand subdaily changes in nutrient processing to fully quantify the impacts of effluent on small streams at different scales. Furthermore, looking at the diel signal without considering conservative transport would overestimate in-stream processing.     

短肢剪力墙应变演化及破坏模式分析

由于应力重分布,钢筋混凝土结构在地震作用下的应力分布变化多端、复杂,其变化过程可从应变分布演化过程来反映.通过追踪6个T形截面短肢剪力墙的应变演化过程,还原了试件在低周反复荷载作用下的应力变化全过程.在上述基础上,对试件的破坏模式做出了准确的分析,进而准确地找出了试件的薄弱部位、提出了一些加固意见,并探讨了平截面假定的适用性.     

Rock magnetism and the Earth's palaeopoles

Summary On the assumption of a constant earth radius the spherical-trigonometric determination of former pole positions depends on the position of the North Pole of today. On the basis of an expanding earth, the determination of the palaeopoles should not be attempted on the present globe. There should rather be used a pole position on a model globe with a reckoning pole which is situated along the present northern direction of the measuring origin and spaced therefrom by its present pole distance. In that way Palaeozoic pole positions formerly determined in the Mid-Pacific shift to northeastern Siberia.

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Zusammenfassung Bei der sphärisch-trigonometrischen Berechnung früherer Pollagen unter Voraussetzung eines konstanten Erddurchmessers spielt die Lage des heutigen Nordpols eine wichtige Rolle. Bei Voraussetzung einer expandierenden Erde darf jedoch die Bestimmung der Paläopole nicht am heutigen Globus erfolgen. Vielmehr ist an einem Modellglobus ein Berechnungspol zu verwenden, der auf der heutigen Nordrichtung des Meßorts in seiner heutigen Poldistanz von ihm entfernt liegt. Auf diese Weise ergeben sich für das Paläozoikum Pollagen in Nordostsibirien an Stelle von Pollagen mitten im Pazifik.

     

Rock magnetism and the reversal of the geomagnetic field

Summary The present paper deals with the inverse polarization of rocks. At present there are two schools of thought to explain the inverse polarization. On the one hand, it is assumed that the geomagnetic field might have been reversed in those periods, when the rock formations took place. On the other it is advocated that it might be due to some intrinsic property of the rocks. To distinguish between the two theories, the author has studied the thermal demagnetization of a large number of rock samples from the Isle of Mull and has come to the conclusion that the inverse polarization is not due to an intrinsic property of the rocks as suggested byNéel, but to the reversal of the geomagnetic field. Some experimental details are also described in the paper.     

Rock creep and the development of the Niagara cuesta

This work addresses the post‐glacial development of the Niagara Escarpment, specifically the east‐facing scarp slopes between Hamilton and Collingwood. The escarpment is one of a series of scarps that shape the Great Lakes Basin. One interpretation suggests that the escarpment has evolved through homoclinal recession to the west. It is therefore viewed as an erosional feature brought about due to fluvial action on the weaker shale formations that underlie the cap rock. However, the deposition of large amounts of drift during the Pleistocene glaciation has resulted in the disruption of the preglacial drainage pattern within the Great Lakes Basin. Therefore, the current drainage is typically orthogonal to the scarp face with an absence of fluvial action along the base. Consequently, the cuesta is experiencing an extremely slow rate of retreat. Conventional thinking on the evolution of the present morphology suggests that it developed rapidly following deglaciation due to periglacial processes. The concept of the escarpment as a relict feature during the Holocene therefore pervades the modern literature. However, the cambering of the cap rock towards the scarp face and the apparent motion of individual joint‐bounded blocks indicates that in the absence of exogenetic processes, a slow development due to endogenetic processes has dominated the modern development of the escarpment. It has been proposed that the present morphology of the cliffed sections may be due to deformation within the shale layers. In order to test this hypothesis, the rheology of the rocks that form the escarpment was tested and compared to the gravitational stresses that would be expected within the rock mass. The results indicate that the compressive strength of the shale layers of the Cabot Head Formation is lower than the expected effective stresses. It is therefore concluded that in the absence of high confining stresses, as would be expected near the cliff face, slow plastic deformation within this formation is occurring. The morphological expression of this deformation is seen in the cambering of the escarpment, the dilation of pre‐existing joints, and the rotation of joint‐bounded blocks. Copyright © 2002 John Wiley & Sons, Ltd.     

The architecture, eruptive history, and evolution of the Table Rock Complex, Oregon: From a Surtseyan to an energetic maar eruption

The Table Rock Complex (TRC; Pliocene–Pleistocene), first documented and described by Heiken [Heiken, G.H., 1971. Tuff rings; examples from the Fort Rock-Christmas Lake valley basin, south-central Oregon. J. Geophy. Res. 76, 5615-5626.], is a large and well-exposed mafic phreatomagmatic complex in the Fort Rock–Christmas Lake Valley Basin, south-central Oregon. It spans an area of approximately 40 km², and consists of a large tuff cone in the south (TRC1), and a large tuff ring in the northeast (TRC2). At least seven additional, smaller explosion craters were formed along the flanks of the complex in the time between the two main eruptions. The first period of activity, TRC1, initiated with a Surtseyan-style eruption through a 60–70 m deep lake. The TRC1 deposits are dominated by multiple, 1-2 m thick, fining upward sequences of massive to diffusely-stratified lapilli tuff with intermittent zones of reverse grading, followed by a finely-laminated cap of fine-grained sediment. The massive deposits are interpreted as the result of eruption-fed, subaqueous turbidity current deposits; whereas, the finely laminated cap likely resulted from fallout of suspended fine-grained material through a water column. Other common features are erosive channel scour-and-fill deposits, massive tuff breccias, and abundant soft sediment deformation due to rapid sediment loading. Subaerial TRC1 deposits are exposed only proximal to the edifice, and consist of cross-stratified base-surge deposits. The eruption built a large tuff cone above the lake surface ending with an effusive stage, which produced a lava lake in the crater (365 m above the lake floor). A significant repose period occurred between the TRC1 and TRC2 eruptions, evidenced by up to 50 cm of diatomitic lake sediments at the contact between the two tuff sequences. The TRC2 eruption was the last and most energetic in the complex. General edifice morphology and a high percentage of accidental material suggest eruption through saturated TRC1 deposits and/or playa lake sediments. TRC2 deposits are dominated by three-dimensional dune features with wavelengths 200–500 m perpendicular to the flow, and 20–200 m parallel to the direction of flow depending on distance from source. Large U-shaped channels (10–32 m deep), run-up features over obstacles tens of meters high, and a large (13 m) chute-and-pool feature are also identified. The TRC2 deposits are interpreted as the products of multiple, erosive, highly-inflated pyroclastic surges resulting from collapse of an unusually high eruption column relative to previously documented mafic phreatomagmatic eruptions.     

大地电磁信号整理分析

小波分析是具有时频多分辨率分析特点的新的信号处理方法,本文应用时间序列反映出大地电磁信号功率谱特性并比较了几种常规实验手段的分析效果,通过小波变换分离出假频所在通道并进行初步除噪,按能量强弱对信号重新截断划分．本文的目的就是尽可能的消除对各组信号不一致的影响因素(局部噪声),提取共性较强的部分并按能量的差异来划分这些信号．     

True Triaxial Stresses and the Brittle Fracture of Rock

This paper reviews the efforts made in the last 100 years to characterize the effect of the intermediate principal stress σ ₂ on brittle fracture of rocks, and on their strength criteria. The most common theories of failure in geomechanics, such as those of Coulomb, and Mohr, disregard σ ₂ and are typically based on triaxial testing of cylindrical rock samples subjected to equal minimum and intermediate principal stresses (σ ₃=σ ₂). However, as early as 1915 Böker conducted conventional triaxial extension tests (σ ₁=σ ₂) on the same Carrara marble tested earlier in conventional triaxial compression by von Kármán that showed a different strength behavior. Efforts to incorporate the effect of σ ₂ on rock strength continued in the second half of the last century through the work of Nadai, Drucker and Prager, Murrell, Handin, Wiebols and Cook, and others. In 1971 Mogi designed a high-capacity true triaxial testing machine, and was the first to obtain complete true triaxial strength criteria for several rocks based on experimental data. Following his pioneering work, several other laboratories developed equipment and conducted true triaxial tests revealing the extent of σ ₂ effect on rock strength (e.g., Takahashi and Koide, Michelis, Smart, Wawersik). Testing equipment emulating Mogi's but considerably more compact was developed at the University of Wisconsin and used for true triaxial testing of some very strong crystalline rocks. Test results revealed three distinct compressive failure mechanisms, depending on loading mode and rock type: shear faulting resulting from extensile microcrack localization, multiple splitting along the σ ₁ axis, and nondilatant shear failure. The true triaxial strength criterion for the KTB amphibolite derived from such tests was used in conjunction with logged breakout dimensions to estimate the maximum horizontal in situ stress in the KTB ultra deep scientific hole.