自平衡法在灌注桩承载力检测中的应用及其有关问题

自平衡法是基于静载荷试验发展而来的建筑桩基检测方法,它可以快速检测隐蔽桩体的极限承载力。文章阐述了自平衡法测桩技术,并通过工程实例,论述了试验桩现场自平衡法实测效果,同时与预估极限承载力进行比较,分析了自平衡法测桩技术中荷载箱位置的设置对于桩基极限承载力的影响。文章还对自平衡法检测应用中需要注意的问题进行了说明。     

Impact of Planetary Wave Reflection on Tropospheric Blocking over the Urals–Siberia Region in January 2008

Planetary wave reflection from the stratosphere played a significant role in changing the tropospheric circulation pattern over Eurasia in mid-January 2008. We studied the 2008 event and compared with composite analysis(winters of 2002/2003,2004/2005, 2006/2007, 2007/2008, 2010/2011 and 2011/2012), when the downward coupling was stronger, by employing time-lagged singular value decomposition analysis on the geopotential height field. In the Northern Hemisphere, the geopotential fields were decomposed into zonal mean and wave components to compare the relative covariance patterns. It was found that the wavenumber 1(WN1) component was dominant compared with the wavenumber 2(WN2) component and zonal mean process. For the WN1 field, the covariance was much higher(lower) for the negative(positive) lag, with a prominent peak around +15 days when the leading stratosphere coupled strongly with the troposphere. It contributed to the downward coupling due to reflection, when the stratosphere exhibited a partially reflective background state. We also analyzed the evolution of the WN1 anomaly and heat flux anomaly, both in the troposphere and stratosphere, during January–March 2008. The amplitude of the tropospheric WN1 pattern reached a maximum and was consistent with a downward wave coupling event influenced by the stratospheric WN1 anomaly at 10 h Pa. This was consistent with the reflection of the WN1 component over Eurasia, which triggered an anomalous blocking high in the Urals–Siberia region. We further clarified the impact of reflection on the tropospheric WN1 field and hence the tropospheric circulation pattern by changing the propagation direction during and after the event.     

Tidal Mixing in the Kuril Straits and Its Impact on Ventilation in the North Pacific Ocean

A numerical study using a 3-D nonhydrostatic model has been applied to baroclinic processes generated by the K ₁ tidal flow in and around the Kuril Straits. The result shows that large-amplitude unsteady lee waves are generated and cause intense diapycnal mixing all along the Kuril Island Chain to levels of a maximum diapycnal diffusivity exceeding 10³ cm²s⁻¹. Significant water transformation by the vigorous mixing in shallow regions produces the distinct density and potential vorticity (PV) fronts along the Island Chain. The pinched-off eddies that arise and move away from the fronts have the ability to transport a large amount of mixed water (∼14 Sv) to the offshore regions, roughly half being directed to the North Pacific. These features are consistent with recent satellite imagery and in-situ observations, suggesting that diapycnal mixing within the vicinity of the Kuril Islands has a greater impact than was previously supposed on the Okhotsk Sea and the North Pacific. To examine this influence of tidal processes at the Kurils on circulations in the neighboring two basins, another numerical experiment was conducted using an ocean general circulation model with inclusion of tidal mixing along the islands, which gives a better representation of the Okhotsk Sea Mode Water than in the case without the tidal mixing. This is mainly attributed to the added effect of a significant upward salt flux into the surface layer due to tidal mixing in the Kuril Straits, which is subsequently transported to the interior region of the Okhotsk Sea. With a saline flux into the surface layer, cooling in winter in the northern part of the Okhotsk Sea can produce heavier water and thus enhance subduction, which is capable of reproducing a realistic Okhotsk Sea Mode Water. The associated low PV flux from the Kuril Straits to the open North Pacific excites the 2nd baroclinic-mode Kelvin and Rossby waves in addition to the 1st mode. Interestingly, the meridional overturning in the North Pacific is strengthened as a result of the dynamical adjustment caused by these waves, leading to a more realistic reproduction of the North Pacific Intermediate Water (NPIW) than in the case without tidal mixing. Accordingly, the joint effect of tidally-induced transport and transformation dominating in the Kuril Straits and subsequent eddy-transport is considered to play an important role in the ventilation of both the Okhotsk Sea and the North Pacific Ocean. This revised version was published online in July 2006 with corrections to the Cover Date.     

2011年桂西长时间低温天气成因分析

利用实况观测资料和NCEP／NCAR再分析资料,通过统计学和天气诊断分析的方法,对桂西2011年1月持续的低温天气进行分析,结果表明：极涡呈偶极型且位于亚洲北部的中心偏东、偏南是此次低温天气维持的环流背景特点;华南沿海的静止锋维持但坡度较大,不利于形成明显的逆温条件,是桂西主要出现阴雨天气而不出现冻雨的主要原因,海拔较高的北部山区局部出现的冻雨天气是由于特殊地形下的逆温层结造成的,维持时间较短：阻塞形势的建立和维持是低温天气维持的主要原因,阻高崩溃、横槽转竖的过程使桂西气温更明显下降;南支槽的两次东移使桂西产生较明显降水,对降温有明显影响。     

Particle tracking experiments on a model of the Okhotsk Sea: Toward oil spill simulation

Particle tracking experiments were conducted for the Sea of Okhotsk using a three-dimensional ocean circulation model, as a step toward the simulation of oil spills. The model’s reproducibility is first examined in detail. Comparison with surface drifter and moored ADCP data shows that the model successfully reproduces the velocity field over the shelves, particularly in the weak stratification period. This is because the current variability is simply determined by integration of the alongshore component of the wind stress over the coast from which arrested topographic waves propagate. Good agreement even in the ice-covered period implies that the neglect of sea ice in the model is not a problem for reproduction of the current over the shelves. Good agreement also supports the correction of ECMWF wind speed by a factor of 1.25. A series of particle tracking experiments was carried out to examine the case of particles released from the Sakhalin oil field at depths of 0 m and 15 m. Regardless of the deployment month and year, most particles at depth 15 m are transported southward along the Sakhalin coast, in accordance with the abrupt intensification of the East Sakhalin Current in October, finally arriving offshore of Hokkaido in November–January. Particles at the surface, which are affected by wind drift in addition to the ocean current, show larger yearly variability. In years when the offshoreward-wind dominates, the particles would be advected out of the mainstream of the current and would not be transported offshore of Hokkaido.     

Observation of the Soya Warm Current using HF ocean radar

Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are 3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs). The current velocity derived from the HF radars shows good agreement with that observed using the drifting buoys. The root-mean-square (rms) differences were found to be less than 20 cm s⁻¹ for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reasonable agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s⁻¹, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 40 km. The surface transport by the SWC shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records at Wakkanai and Abashiri. Deceased.     

碎屑流高风险区桩群防护结构优化布局研究

桩群是一种可有效耗散碎屑流运动能量,抑制碎屑流运动距离及速度的山地灾害防护结构。在碎屑流沟口与受灾体之间构建一组桩群减速带,可达到保护受灾体的目的。以物理模型试验为基础,开展弧型桩群、方型桩群和圆型桩群的沟槽型碎屑流冲击动力响应研究。讨论了3种不同类型的桩群对沟槽型碎屑流运动形态的影响,进一步开展弧型桩群的结构优化研究。结果表明：采用桩群结构可有效减小沟槽型碎屑流堆积距离并抑制其运动速度;3种不同形状桩群之间,弧型桩与方型桩的拦挡效果明显优于圆型桩;弧型桩由于凹槽式外型,对沟槽型碎屑流堆积面积、淤埋深度的抑制效果稍优于方型桩;在相同高度、直径等几何参数下,弧型桩体积比圆型桩小22.6%,比方型桩小39.2%,因此弧型桩的制作成本也相对较低;弧型桩排数从1排增加到3排,桩群拦挡率分别提升7.2%、4.5%;适量增加槽口与桩之间距离Ld可以有效提高弧型桩群防护结构的能量耗散效率。该研究可为桩群在沟槽型碎屑流防治工程中的应用提供理论及技术支持。     

Time-series sediment trap record of alkenones from the western Sea of Okhotsk

C₃₇–C₃₉ alkenones were measured in time-series sediment trap samples collected from August 1998 to June 2000 at two depths in the seasonal sea ice region of the western Sea of Okhotsk, off Sakhalin, in order to investigate alkenone production and water-column processes in the region. Measurable export fluxes of alkenones are ranged from < 0.1 to 5.8 μg/m²/day and clearly showed that the alkenone production was restricted to autumn. In 1998, maximum export flux of alkenones occurred in September when surface water column was well stratified with low nutrients in the surface mixing layer. In the next year, the maximum flux is observed in October. Comparison between alkenone temperature and satellite based sea surface temperature (SST) shows that the estimated alkenone temperatures in August 1998 were found to be  10 °C lower than the temporal satellite SST, suggesting that alkenones are produced in surface to subsurface thermocline layers during the period. Annual mean flux of alkenones is lower in the lower traps than that of the upper traps, suggesting rapid degradation of alkenones in water column, but the U^K₃₇′ value is not significantly altered. This study indicates that U^K₃₇′ values preserved in the surface sediments off Sakhalin reflect the seasonal temperature signal of near surface water, rather than annual mean surface temperature.     

GPS time-series and its response to M S=8.1 Kunlunshan earthquake

In this paper, observation data in 25 GPS reference stations of China have been analyzed by calculating GPS position coordinate time-series with GIPSY. Result shows there is an obvious trend variation in such time-series. The trend variations of time series along the longitude and latitude coordinate reflect the motion of each position in the global-plate, in which the trend variation in the vertical direction reveals some large-scale construction information or reflects the local movement around the positions. The analysis also shows that such time-series have a variation cycle of nearly 1.02 a, but the reason still remains to be further studied. At the end of this paper, response of the time-series of M _S=8.1 Kunlunshan earthquake was analyzed, and the seismogenic process of M _S=8.1 Kunlunshan earthquake, according to the time proceeding and the feature of anomaly, was divided into 3 phases—changes in blocks with forces, strain accumulation, quick accumulation and slow release of energy. At the initial stage of seismogenic process of M _S=8.1 earthquake and at the imminent earthquake, coseismic process as well as during the post earthquake recovery, anomaly in vertical direction is always in a majority. The anomalous movement in vertical direction at the initial stage resulted in a blocking between faults, while at the middle stage of seismogenic process, the differential movement between blocks are in a majority, which is the major reason causing energy accumulating at the blocking stage of faults. Foundation item: National Natural Science Foundation of China (40074024 and 40304002).     

近40年5-6月东北亚和北半球其他区域阻塞高压活动特征及其联系

基于美国环境预报中心/国家大气研究中心(NCEP/NCAR-Ⅰ)再分析资料,按照国际通行的阻塞高压(阻高)定义,采用计算机自动识别和天气图人工主、客观相结合的检测方法,获得了1979—2018年5月和6月逐日北半球中高纬度阻高活动的无缝隙分布;并利用线性相关和信息流因果关系等统计方法,研究了东北亚(鄂霍次克海)阻高与北半球其他阻高活动区特征及其联系。根据阻高活动集中程度与占北半球活动总天数的百分比,选定8个5月阻高主要活动区和10个6月阻高主要活动区。从统计结果来看,5月北太平洋、北美和乌拉尔山阻高活动占前3位,6月东北亚阻高活动天数跃升第1位。值得注意的是,初夏在贝加尔湖以南、青藏高原以北地区出现了明显的阻塞形势,称为青藏高原北阻高。5月和6月北半球各阻高活动中心集中的纬度分布,自西向东具有"正弦波"特征,其主要活动区引起的同期北半球500 hPa高度场的异常虽不尽相同,但均具有一定的遥相关特征;5月和6月东北亚阻高活动天数的年际变化分量具有明显的相对独立性。5月东北亚阻高是6月贝加尔湖阻高活动年际变化的稳定影响源,是6月青藏高原北阻高活动年际变化的不稳定影响源;唯有5月北太平洋阻高...