Stress Analyses in the Epicentral Area of Nový Kostel (Western Bohemia)

The focal mechanisms of events from three micro-earthquake swarms (swarm in the years 1985/86, swarm of December 1994, and swarm of January 1997) in the epicentral area of Nový Kostel (West Bohemia region) were used as input data for stress analyses. The simple graphical method of Angelier and Mechler (1977) and inversion by the program BRUTE3 (Hardcastle and Hills, 1993) were applied to the data collections. The results of the stress analyses for the 1985/86 swarm and for the swarm of December 1994 are similar. For the January 1997 swarm, the results of the analyses differ from those for older swarms. The axis of maximum extension is oriented in the NE-SW direction and is subhorizontal, the axis of maximum compression is oriented in the NW-SE direction and perspicuously dips towards SE. These results are similar to older results of stress analyses carried out for the 1985/86 swarm (Antonini, 1988; Sonnleitner,1993). They are also consistent with most of other published results of stress analyses conducted at different sites in the western part of the Bohemian Massif. The orientation of the principal stresses confirms the sinistral strike-slip movement along the Nový Kostel-Poátky-Zwota line (the trend is about 355°) defined by the epicentres of the micro-earthquakes. The eastern tectonic limit of the Cheb Basin (and other respective parallel faults ) could be characterised by normal rather than strike-slip faulting.     

福建厦门地区中、新生代构造应力场研究

本文通过野外构造形变资料的研究,确定了厦门地区中生代的两期（侏罗纪、白垩纪）构造应力场及其主应力方向;利用最新一期共轭剪节理和震源机制解资料,确定了第四纪以来的构造应力场及其主应力方向。最大主压应力轴的优选方位分别为:侏罗纪SE138°,∠8°,白垩纪SW205,∠12°,第四纪以来NW312°,∠21°。 采用石英错密度法,估算了中生代古构造应力值,侏罗纪为88.5MPa,白垩纪为81.5MPa。利用岩石力学声发射技术,测定了现代构造应力大小,在标高为3——-151m（埋深为18——151m）的范围内,最大主压应力值为2.55——16.2MPa,最小主压应力值为1.1——10.1MPa。     

The Boussinesq problem for soils with bounded non-homogeneity

The response of a compressible continuously non-homogeneous elastic soil to a static vertical point load on its surface is analytically investigated by using classical integral transform techniques and the extended power series method for obtaining the solution in the transform domain. The non-homogeneity is described by means of a depth-function which is non-zero at the surface and bounded at infinity and is capable in modelling both increasing and decreasing soil stiffness with depth. The influence of non-homogeneity on the displacements and stresses at the surface and in the interior is examined over a wide range on the governing parameters. © 1998 John Wiley & Sons, Ltd.     

侧压系数对圆孔周边松动区破坏模式影响的数值试验研究

利用岩石破裂过程分析软件RFPA2D,对岩体中的圆孔周边的变形及非线性渐进破坏特征、巷道周边关键部位的应力变化进行了分析,研究了应力场中侧压力系数对围岩应力场分布的影响。研究指出,侧压系数 对应力场分布及圆孔周边松动区的破坏特征起决定作用。当 ≤1时,顶板的塑性区和卸压范围较大,但顶板挠度却较小;当 时,顶板的塑性区和卸压范围较小,但顶板挠度却较大。对于进一步深入理解深部岩体中巷道破坏失稳机制并采取有效的加固措施等具有重要的理论和实践意义。     

Variability of internally generated turbulence in an estuary,from 100 days of continuous observations

We present detailed observations of internally generated turbulence in a sheared, stratified natural flow, as well as an analysis of the external factors leading to its generation and temporal variability. Multi-month time series of vertical profiles of velocity, acoustic backscatter (0.5 Hz), and turbulence parameters were collected with two moored acoustic Doppler current profilers (ADCPs) in the Hudson River estuary, and estuary-long transects of water density were collected 30 times. ADCP backscatter is used for visualization of coherent turbulent structures and evaluation of surface wave biases to the turbulence measurements. Benefits of the continuous long-term turbulence record include our capturing: (1) the seasonality of turbulence due to changing riverflow, (2) hysteresis in stratification and turbulence over the fortnightly cycle of tidal range, and (3) intermittent events such as breaking internal waves. Internal mixing layers (IMLs) are defined as turbulent regions above the logarithmic velocity layer, and the bottom boundary layer (BBL) is defined as the continuously turbulent range of heights above the bed. A cross-correlation analysis reveals how IML and BBL turbulence vary with stratification and external forcing from tidal range, river flow, and winds. Turbulence in both layers is maximal at spring tide and minimal when most stratified, with one exception—IML turbulence at a site with changing channel depth and width is maximal at times of maximum stratification and freshwater input.     

用双曲线切线模量方程计算地基非线性沉降

提出了一种利用原位试验成果求解非均质非线弹性地基最终沉降的新方法。对分层原状土载荷试验或螺旋板试验成果进行双曲线拟合,建立分层原状土切线模量与竖向附加应力的关系方程;在沉降计算公式中引入附加应力修正系数,以考虑基础埋深、地基非均质非线性特征等因素对应力分布的影响;利用双曲线切线模量方程及附加应力弹性解,可准确求解地基的总沉降。通过对几个压板载荷试验成果的拟合分析,得出了各土类的双曲线切线模量方程,用于求解地基在各级荷载下的沉降。计算结果表明,计算值与实测值吻合得很好。该方法原理简单、参数可靠、结果准确,为地基沉降计算开辟了一条新途径。     

正交各向异性岩体钻孔周围应力分布的应力变分法分析

利用孔径变形法和孔壁应变法测量地应力必然涉及到钻孔周围岩体应力的分布规律,由于各向异性岩体孔周应力的分布复杂,很难用求解偏微分方程的方法得到应力分布的解析表达式,而应力分布又影响着地应力分析结果的准确性。通过构造应力函数,采用应力变分法对钻孔周围的应力进行求解,为准确分析各向异性岩体的地应力提供理论基础。     

Development of bedforms due to waves blocked by a counter current

Experiments are conducted in a laboratory flume on the propagation of a surface wave against unidirectional flow with a sediment bed. This article presents the spatial variation of bedforms induced by the wave-blocking phenomenon by a suitably tuned uniform fluid flow and a counter-propagating wave. The occurrence of wave-blocking is confirmed by finding a critical wave frequency in a particular flow discharge in which the waves are effectively blocked and is established using the linear dispersion relation. The purpose of this work is to identify wave-blocking and its influence on the development of bedforms over the sediment bed. Interestingly bedform signatures are observed at a transition of bedforms in three zones, with asymmetric ripples having a steeper slope downstream face induced by the incoming current, followed by flat sand bars beneath the wave-blocking zone and more symmetric ripples below the wave-dominated region at the downstream. This phenomenon suggests that the sediment bed is segmented into three different regions of bed geometry along the flow. The deviations of mean flows, Reynolds stresses, turbulent kinetic energy, and power spectral density due to the wave-blocking phenomenon are presented along the non-uniform flow over sediment bed. The bottom shear stress, bed roughness and stochastic nature of the bedform features are also discussed. The results are of relevance to engineers and geoscientists concerned with contemporary process as well as those interested in the interpretation of palaeoenvironmental conditions from fossil bedforms. © 2019 John Wiley & Sons, Ltd.     

基于地应力边界条件的复杂边坡抗滑桩支护设计研究

复杂边坡稳定性问题一直是岩土工程界重点研究的问题之一,提高复杂边坡安全系数的方法有很多,其中采用抗滑桩支护是常用手段之一。以安徽省某高速公路复杂边坡为研究对象,采用套孔应力解除法对该边坡岩土体进行了地应力测试,以测试结果作为有限元分析的边界条件,分别对该边坡加固前和采用抗滑桩加固后两种工况进行数值分析,得到有代表性的有限元分析结果;并对有限元的计算出位移结果和实测位移进行了对比。分析表明,未采用抗滑桩支护的边坡,会产生局部应力过分集中、整体变形和水平向位移较大、塑性区贯通等不利于边坡稳定的危险状况。采用了抗滑桩支护后,贯通的塑性区消失,边坡变形和位移减少,应力分布趋于均匀,安全系数大幅度提高。有限元计算出的位移结果和实测位移十分接近,匹合度较好,从而说明了有限元分析手段的可靠性。     

马坑山公路隧道岩爆预测研究

岩爆是高地应力条件下地下洞室开挖过程中经常遇到的一种动力失稳的地质灾害,直接威胁施工人员和设备的安全。论述了岩爆的定义、特征及发生机理,应用国内外相关岩爆判据判定和理论分析,提出对马坑山隧道开挖过程中是否会产生岩爆做出了最终判定。