动刚度和动力触探在强夯地基检测中的应用

随着碎石土强夯地基的推广应用，解决如何对其进行快速有效地检测，提供其准确的强度及变形参数问题，具有重要的经济及安全意义。提出了一种利用平板静力载荷试验、动力触探、地基动刚度测试三种基本手段，建立相关数学模型，主要应用后两种手段进行联合检测的新思路。并将相关数学模型以经验公式的形式进行了总结，对碎石土强夯地基的检测具有指导意义。     

应变能-莫尔准则及其在岩石材料中的应用

本文应用应变能密度与三向应力圆的等价关系,分析修正了莫尔准则,提出用任意确定静水压力下不同洛德参数的极限莫尔圆包络曲线簇作准则线,即谓之为应变能-莫尔准则线,并引用岩土真三轴试验资料进行验证;最后还得出应变能-莫尔屈服条件,分析了屈服曲面和屈服轨迹的形状等。     

Numerical comparison of different convergent plate contacts: subduction channel and subduction fault

At convergent plate boundaries, the properties of the actual plate contact are important for the overall dynamics. Convergent plate boundaries both mechanically decouple and link tectonic plates and accommodate large amounts of strain. We investigate two fundamental physical states of the subduction contact: one based on a fault and the other based on a subduction channel. Using a finite element method, we determine the specific signatures of both states of the subduction contact. We pay particular attention to the overriding plate. In a tectonic setting of converging plates, where the subducting plate is freely moving, the subduction channel reduces compression relative to the fault model. In a land-locked basin setting, where the relative motion between the far field of the plates is zero, the subduction channel model produces tensile stress regime in the overriding plate, even though the amount of slab roll-back is small. The fault model shows a stronger development of slab roll-back and a compressive stress regime in the upper plate. Based on a consistent comparison of fault and channel numerical models, we find that the nature of the plate contact is one of the controlling factors in developing or not of backarc extension. We conclude that, the type of plate contact plays a decisive role in controlling the backarc state of stress. To obtain backarc extension, roll-back is required as an underling geodynamic process, but it is not always a sufficient condition.     

塔里木西南缘新太古代变质辉长岩脉的锆石SHRIMP U-Pb定年及其地质意义

在塔里木西南缘发现多条变质辉长岩脉,经稀土和微量元素分析,辉长岩岩脉具有稀土总量较低、轻稀土和大离子亲石元素富集,重稀土和高场强元素亏损的特征。通过锆石SHRIMP法U-Pb测年,6个点207Pb/206Pb加权年龄平均值为(2675±12)Ma(MSWD=0.20);根据9个点获得的不一致曲线上交点年龄为(2671±13)Ma、下交点年龄为(287±16)Ma(MSWD=0.91)。2675Ma权重年龄或不一致曲线上交点2671Ma年龄代表变质辉长岩的结晶年龄;下交点(287±16)Ma年龄代表变质年龄。塔里木西南缘新太古代变质辉长岩脉的发现,证实塔里木西南缘存在太古宙古陆核,提供了华北克拉通新太古代古陆核裂解的岩浆活动记录,为该区地层划分对比以及古陆核早期构造演化提供了重要信息。     

地震波散射研究回顾与展望

地震波散射是地球物理学中一个非常重要的研究领域,其进展对人们正确认识和了解地球深部的细节及物性具有重大意义,对地球动力学的研究也具有不可忽视的推动作用。这里从地震波散射的理论和方法研究二个方面,对地震波散射研究的进展作评述。首先回顾了地震波散射的基本概念、研究历程及研究的各个方面,对散射理论进行了系统评述,同时对先辈们关于散射波数值模拟的情况进行了总结。     

陆地声呐法在探查单个溶洞方面的优势

基于地震反射法的陆地声呐法,在预报探查溶洞等方面成功地进行了2个工区的工作,取得了很好的效果,这是由于其接近于零震-检距的工作布置,用锤击激震可接收10~4 000 Hz的超宽频带的接收等特点所决定。无论在地面上探查中、小溶洞方面(查找的溶洞径深比可小于1∶15),还是在隧道施工地质预报方面都有很大优势。     

Tectonic and eustatic control on the distribution of black-shale source beds in the Wufeng and Longmaxi formations (Ordovician-Silurian),South China

It is known that high-quality, black-shale source rocks occur in the uppermost Ordovician Wufeng Formation and in the lowermost Silurian Longmaxi Formation in South China. Hence, it is important to understand their lithostratigraphy and the controls on their deposition. A review of lithostratigraphic criteria for subdividing the two adjacent formations provides new regional correlations between the formations and related stratigraphic successions and facies. Both the black shales and the related, overlying flysch deposits at the Ordovician-Silurian transition in South China appear to have migrated northwestward in time and space, reflecting probable flexural control in a foreland basin that developed in response to subduction-type orogeny southeast of the Yangtze block. The black shales also contain K-bentonites from explosive, felsic-intermediate volcanism, the distribution of which also supports orogeny to the southeast. Finally, the analysis of sequence stratigraphy, which shows that the initiation of transgressive system tracts (TST) and condensed section (CS) in the related third-order sequences coincided with the two black-shale horizons respectively, indicates that the main controlling factors for the deposition of the Ordovician-Silurian black shales in South China are (1) northwestwardly migrating, foreland-basin subsidence caused by deformational loading related to episodic accretion of the Cathaysia block to the Yangtze block during this period, and (2) the anoxic, sediment-starved water column caused by rapid rise of the sea-level during the two successive phases of third-order global sea-level rise near the Ordovician-Silurian transition in South China. In future exploration for hydrocarbon source rocks in the area, it is important to consider likely flexural and eustatic causes for subsiding, deep, anoxic seas in recognizing other source rock intervals, and our understanding of the Wufeng and Longmaxi formations may serve as models for future source rock exploration. __________ Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6): 818–827 [译自: 地球科学—中国地质大学学报]     

The potential influence of subduction zone polarity on overriding plate deformation, trench migration and slab dip angle

A geodynamic model exists, the westward lithospheric drift model, in which the variety of overriding plate deformation, trench migration and slab dip angles is explained by the polarity of subduction zones. The model predicts overriding plate extension, a fixed trench and a steep slab dip for westward-dipping subduction zones (e.g. Mariana) and predicts overriding plate shortening, oceanward trench retreat and a gentle slab dip for east to northeastward-dipping subduction zones (e.g. Chile). This paper investigates these predictions quantitatively with a global subduction zone analysis. The results show overriding plate extension for all dip directions (azimuth α = − 180° to 180°) and overriding plate shortening for dip directions with α = − 90° to 110°. The wide scatter in data negate any obvious trend and only local mean values in overriding plate deformation rate indicate that overriding plate extension is somewhat more prevalent for west-dipping slabs. West-dipping subduction zones are never fixed, irrespective of the choice of reference frame, while east to northeast-dipping subduction zones are both retreating and advancing in five out of seven global reference frames. In addition, westward-dipping subduction zones have a range in trench-migration velocities that is twice the magnitude of that for east to northeastward-dipping slabs. Finally, there is no recognizable correlation between slab dip direction and slab dip angle. East to northeast-dipping slabs (α = 30° to 120°) have shallow (0–125 km) slab dip angles in the range 10–60° and deep (125–670 km) slab dip angles in the range 40–82°, while west-dipping slabs (α = − 60° to − 120°) have shallow slab dip angles in the range 19–50° and deep slab dip angles in the range 25–86°. Local mean deep slab dip angles are nearly identical for east and west-dipping slabs, while local mean shallow slab dip angles are lower by only 4.7–8.1° for east to northeast-dipping slabs. It is thus concluded that overall, there is no observational basis to support the three predictions made by the westward drift model, and for some sub-predictions the observational basis is very weak at most. Alternative models, which incorporate and underline the importance of slab buoyancy-driven trench migration, slab width and overriding plate motion, are better candidates to explain the complexity of subduction zones, including the variety in trench-migration velocities, overriding plate deformation and slab dip angles.