岩质边坡平面滑动锚固方向角的三维优化方法

以岩质边坡中常见的平面滑动为研究对象,研究其最优锚固方向角的计算方法。将锚索自由段单位长度能提供的最大抗滑增量作为目标控制变量,将坡面和滑动面特征参数与锚索设计参数作为优化控制自变量,通过坐标系转换得到的线性方程组对锚索的预拉力进行分解,并根据锚索支护时的三维模型建立了锚索自由段长度的优化公式,进而推导了用于锚固方向角三维优化的新计算方程。在该方程的基础上借助MATLAB软件中的fmincon函数对锚索加固方向不受限制时的锚固方向角进行了优化。最后通过锚固方向角敏感性分析与工程实例分析相结合,证明了推荐的最优锚固方向角计算方法的有效性与先进性。新方法有效地解决了边坡坡面与滑动面走向存在夹角时最优锚固方向角的求解问题,可进一步提高锚索的锚固效益,降低边坡的支护费用。      

惠斯通电桥教学电路的分析

在惠斯通电桥原理电路的基础上，讨论了教学实验中自组电桥测量电路的仪器选择，举例分析了自组电桥测量电路的使用和测量结果，指出不同自组电桥测量电路在教学应用中的优点，为实验教学中突出教学重点而选择电路提供参考。     

Engineering geological investigations for the foundations of large structures-examples of a concrete dam and a long bridge in Portugal

The safety of large structures requires adequate foundations, which implies a good knowledge of the geological and geotechnical conditions of the respective ground. In general, that is only possible through engineering geological studies which include proper site investigation techniques, adapted to the nature of the ground (rock mass or soil) and to the associated engineering problems. The paper illustrates the studies carried out for the design of the foundations of Ribeiradio 76 m high concrete gravity dam in a difficult rock mass and of Vasco da Gama Bridge, 13 km long, crossing the Tagus River in Lisbon, Portugal, through piles 75 m deep.     

Combined Bearing Capacity of Spudcans on a Double Layer Deposit of Strong-Over-Weak Clays

An extreme sea storm process can lead to a jack-up rig under the combined loading condition of vertical load(V), horizontal load(H), and moment(M) to have stability problems. This paper presents the analysis of combined bearing capacities of a circular spudcan on layered clays with a strong layer overlying a comparatively weaker layer. Numerical models combined with displacement-based load tests, swipe tests, and constant ratio displacement probe tests are adopted to calculate the uniaxial bearing capacities, failure envelopes in combined V-H, V-M planes, and failure envelopes in a combined V-H-M load space, respectively. A parametric study on the effects of vertical load level V, the layer strength ratio s_u,t/s_u,b, and the hard layer thickness t_1 on the bearing capacities is then performed. Results show that the vertical load level is a key factor that influences the values of H and M and the size of the H-M failure envelope. The existence of the underlying weak clay decreases the bearing capacities in all directions, and the vertical capacity Vult is affected more than the horizontal(H_ult) and moment(M_ult) capacities based on a single uniform deposit. The influence of the underlying weak clay on H-M failure envelope is mainly shown where H and M are coupled in the same direction. In contrast, little difference is observed when H and M are coupled in opposite directions.     

Parameter analysis of composite pile foundation in bridge foundation

In the current theory of bridge foundation design,all of the loads above the cap are loaded by the pile,and the bearing capacity of the soil among piles is not taken into account.In order to analyze the bearing capacity of the soil among piles in bridge pile foundation,a model of pile foundation is established based on a bridge foundation which is under construction,and by the finite element analysis software ANSYS.According to the results of finite element analysis(FEA)and current bridge foundation design theory,a feasible composite pile foundation which can be applied in the design of bridge foundation,is recommended.Additionally,a number of modifications are made to the original design.It was confirmed that these modifications derived from numerical simulations can improve the performance of the foundation.     

Formation mechanism of a rainfall triggered complex landslide in southwest China

This case study is about a landslide that occurred after 4 days of heavy rainfall,in the morning of June 29,2012,in Cengong County,Guizhou Province of China,geographical coordinated 108°20′-109°03′E,27°09′-27°32′N,with an estimated volume of 3.3×106 m3.To fully investigate the landslide process and formation mechanism,detailed geotechnical and geophysical investigations were performed including borehole drilling,sampling,and laboratory tests coupled with monitoring of displacement.Also,a combined seepage-slope stability modeling was performed to study the behavior of the landslide.After the heavy rainfall event,the sliding process started in this area.The landslide development can be divided into different parts.The man-made fill area,spatially distributed in the south side of the landslide area with low elevations,slid first along the interface between the slope debris and the strongly weathered bedrock roughly in the EW direction.Consequently,due to severe lateral shear disturbance,the slope in the main sliding zone slid next towards the SW direction,along the sliding surface developed within the strongly weathered calcareous shale formation located at a depth of 25-35 m.This means it was a rainfall triggered deep-seated landslide.Finally,retrogressive failure of a number of upstream blocks occurred,which moved in more than one direction.The initial failure of the man-made fill area was the‘engine’of the whole instability framework.This artificial material with low permeability,piled up in the accumulation area of surface and sub-surface and destroyed the drainage capacity of the groundwater.The numerical modeling results agreed with the analysis results obtained from the laboratory and field investigations.A conceptual model is given to illustrate the formation mechanism and development process of the landslide.     

Decadal variability of chlorophyll a in the South China Sea: a possible mechanism

Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1998-2002). We analyzed decadal variability of chlorophyll a by comparing the products of the two observation periods. The relationships of variability in chlorophyll a with sea surface wind speed (SSW), sea surface temperature (SST), wind stress (WS), and mixed layer depth (MLD) were determined. The results indicate that there is obvious chlorophyll a decadal variability in the SCS. The decadal chlorophyll a presents distinct seasonal variability in characteristics, which may be as a result of various different dynamic processes. The negative chlorophyll a concentration anomaly in January was associated with the warming of SST and a shallower MLD. Generally, there were higher chlorophyll a concentrations in spring during the SeaWiFS period compared with the CZCS period. However, the chlorophyll a concentration exhibits some regional differences during this season, leading to an explanation being difficult. The deepened MLD may have contributed to the positive chlorophyll a concentration anomalies from the northwestern Luzon Island to the northeastern region of Vietnam during April and May. The increases of chlorophyll a concentration in northwestern Borneo during May may be because the stronger SSW and higher WS produce a deeper mixed layer and convective mixing, leading to high levels of nutrient concentrations. The higher chlorophyll a off southeastern Vietnam may be associated with the advective transport of the colder water extending from the Karimata Strait to southeastern Vietnam.     

东营市土地资源承载能力分析

本文通过分析东营市土地资源的特点,经济和社会发展对土地的需求,以及土地后备资源的潜力,研究了东营市土地资源承载能力,提出了实现东营市耕地总量平衡的措施。     

Ground subsidence mechanism of a filling mine with a steeply inclined ore body

Long-term field monitoring finds that serious surface subsidence can still occur even if the high strength cemented fill method is adopted. Combining the results of numerical simulations with global position system(GPS) monitoring, we took a typical filling mining mine with a steeply inclined ore body as an example, and explored its ground subsidence mechanism. The results show that the ground subsidence caused by the mining of steep ore body is characterized by two settlement centers and a sign...     

高压旋喷注浆在桥梁地基加固中的应用

国道108线K9+69410沙河立交小桥地基采用高压旋喷注浆法加固.系统介绍了工程概况、设计方案、注浆施工,并通过现场试验证明了高压旋喷注浆法加固桥梁地基是一项成功实践.     

秦巴山区软岩地基桥桩承载性状试验研究

为了研究软岩地基桥桩的荷载传递性状、破坏机理,并获取在该地质条件下更为可靠的桩基计算参数,对秦巴山区软岩地基3根钻孔灌注试桩进行竖向静载试验.结果表明:秦巴山区软岩地基桥桩试桩荷载沉降曲线呈陡降型,实测竖向极限承载力为20500kN,桩的破坏方式为桩身材料强度破坏;淤泥质亚黏土地层中的碎石起到一定的骨架作用,增强了此地层桩极限侧阻力,发挥极限侧阻力所需的桩土(岩)相对位移为4~8mm;强风化砾岩表现为加工软化型,发挥极限侧阻力所需的桩土(岩)相对位移为3~8mm;中风化砂砾岩表现为明显的加工硬化型,所需的桩岩相对位移大,且桩极限侧阻力的特征点不明显;淤泥质亚黏土地层桩侧阻力占总荷载的60%~70%,随着桩顶荷载的逐步加大,该地层桩侧阻力所占比例不断下降,而嵌岩段桩侧阻力所占比例逐渐上升,达到55%~65%,嵌岩段桩侧阻力沿桩深的分布曲线表现出非线性的特征;试桩为端承摩擦桩,桩端阻力约占桩顶荷载的20%左右,且未充分发挥,在上部结构允许的沉降范围内,适当增加桩端的沉降有利于端阻力的发挥;桩侧阻力先于端阻力发挥,建议单桩承载力设计时分别采用不同的端阻力和侧阻力安全系数.     

基于双重注意力机制的滑坡识别方法优化

随着计算机视觉技术的发展,通过卫星图像深度学习进行滑坡识别的研究正在逐步展开。通过引入双重注意力机制,提出了一种基于卷积神经网络的滑坡图像识别优化算法。基于统计的2 200张滑坡图像数据集,探讨了10种网络结构及4种注意力机制对滑坡识别结果的影响,并通过比例为4∶1的训练集和测试集进行滑坡识别,验证了本文方法的有效性。结果表明：ResNet结构相较于其他网络结构表现更为优秀,就该算例而言,ResNet-101结构具有最高的召回率、精确率和F1度量。融入了双重注意力机制的卷积神经网络相较于单个神经网络而言,滑坡识别的精确率更大,且滑坡边界分割结果更接近于真实的滑坡边界,其中,ResNet-101+DAN模型为最优模型。相较之下,单个神经网络无法克服图像噪声的影响,图像分割结果不佳。     

Experimental investigation on the failure mechanism of a rock landslide controlled by a steep-gentle discontinuity pair

A type of rock landslide is very common in practical engineering, whose stability is mainly controlled by the rock bridge between the steep tensile crack at the crest and the low-inclination weak discontinuities at the toe(namely, ligament is the term for the locking section in the slope). To obtain a deeper understanding into the failure process of this kind of landslide, twenty-four physical slope models containing a steep-gentle discontinuity pair(a steep crack in the upper part and a low-inclination discontinuity in the lower part) were tested by applying vertical loads at the crests. The results indicate that the inclination angle of the ligament(θ) has great influence on the failure and stability of this type of rock slope. With the change of θ, three failure patterns(five subtypes) concerning the tested slopes can be observed, i.e., tensile failure of the ligament(Type 1), tension-shear failure of the ligament(Type 2) and two-stage failure of the main body(Type 3). The failure process of each failure mode presents five stages in terms of crack development, vertical load, horizontal/vertical displacements and strains in the ligaments. The specific range of the ligament angle between different failure patterns is summarized. The discussion on the failure resistances and ductility of different failure patterns, and the guiding significances of the experimental findings to the stability evaluation and the reinforcement were conducted.     

The mechanism of a new type of modified clay controlling Phaeocystis globosa growth

Phaeocystis globosa is a harmful algal bloom(HAB) species worldwide.Using modified clay(MC) to control HAB s and to mitigate their adverse effects is currently a commonly used method in China.In this paper,the effects of oxidized composite modified clay(OXI-MC) on P.globosa were studied from different perspectives.The results show that the OXI-MC could effectively remove P.globosa and inhibit both the growth of residual algal cells and the formation of new colonies.The P.globosa algal biomass removal efficiencies after 3 h reached 90% at a dose of 0.1 g/L,and the number of colonies with different particle sizes was greatly reduced.Compared with those of the control,the superoxide dismutase(SOD)activity,catalase(CAT) activity,and malondialdehyde(MDA) content of the residual algae significantly increased,indicating that OXI-MC caused oxidative stress in the algal cells.In addition,we evaluated the effects of OXI-MC on the photo synthe sis of residual microalgae and found that the maximal photochemical efficiency of photosystem II(PSII) under dark adaptation(F_v/F_m) and actual photochemical efficiency of PSII(cDPSII) decreased,severely damaging the photosynthesis efficiency,implying that OXI-MC effected the photosynthesis system of P.globosa.The results of this study clarify that OXI-MC could remove the most of algal cells and break up the colonies of P.globosa by collision,flocculation,and releasing active substances,as well as inhibit effectively the growth and colony formation of residual P.globosa by causing oxidative stress,reducing photosynthesis activity,accelerating the degradation of polysaccharides,and inhibiting the formation of colonies.     

西湖凹陷天台斜坡带火山机构三维雕刻及成因机制解析

西湖凹陷天台斜坡区火成岩发育尤为丰富,其发育与分布对盆内储层改造、构造演化都有着重要影响。依据区内地震特征和构造环境,划分出中心式、裂隙式2种喷发类型;采用振幅－方差体地震属性分级－拾取－融合技术,系统刻画区内火成岩的三维时空展布以及火山喷发时期,发现区内火成岩具有始新世至中新世多期间歇性发育特征,且火山机构富集于天台斜坡西南部;在区内建立了中心式和裂隙式2种喷发模式,认为这些模式的建立对于正确预测火成岩的分布具有重要意义;最后对火成岩的成因机制进行了解析与探讨,发现区内火山活动与板块构造运动相互影响、火山的时空展布与断裂也具有一定的配置关系,认为裂隙式喷发可能会形成优势的油气运移通道,中心式喷发则有利于形成良好的储集空间。基于此,我们将更容易找到区内有效的火成岩储层,对油气勘探具有重要的指示作用。      

Finite element analysis on impact of foundation treatment in bridgehead transition section upon bridge piles

In order to decrease relative settlement, foundation treatment plays an extremely important role in bridgehead transition section, especially, the situation of building the bridge piles firstly, and th...     

Engineering geological assessment for route selection of railway line in geologically active area: A case study in China

The Cheng-Lan railway links Chengdu, a central city in Southwestern China, and Lanzhou, a central city in Northwestern China. The railway passes through the Longmenshan fault zone (Wenchuan earthquake happened there on May 12, 2008), Minjiang fault zone, and Dongkunlun fault zone, which are all active. It runs over the Yangtze River and the Yellow River, and crosses high mountains and deep valleys. There exists, along the railway’s alignment, different kinds of strata of hard granite and soft, weak metamorphic rocks such as carbonaceous slate, schist, and phyllite. It is, therefore, a key issue for such an infrastructure construction to assess the engineering geological conditions and risks, so as to mitigate or avoid possible georisks and to offer optional designs. Geological survey and georisk assessment along the railway corridor are carried out. Special attention is given to active faults, earthquakes and seismic zones. Based on these, discussions about geological aspects for route selection of the railway are conducted and countermeasures for georisk control are proposed accordingly. Main conclusions are achieved as follows: (1) Geohazards such as landslides, rockfalls and debries flows dominate both the route selection of the railway and the engineering structures (e.g., tunnels or bridges) adopted; (2) Tunnel has been proved to be an excellent structure for linear engineering in geologically active area; and (3) In the case where avoiding is impractical, necessary protection measures should be taken to engineering slopes in high earthquake intensity areas, especially the area with earthquake of Ms. 8 or greater.     

Failure mechanism of a large-scale composite deposits caused by the water level increases

The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area. Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case, the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation, the failure mechanism of the composite deposits during...     

Outburst mechanism of Yindapu Glacial Lake in Tibet

At present, the mechanism research on glacial lake outburst mainly focuses on the ice quake and ice landslide, etc. To some glacial lakes, the seepage deformation is the dominant factor in outburst process. Taking the Yindapu Glacial Lake in Tibet as an example, using SEEP/W module of FEM software （ GEO-STUDIO）, the authors analyzed seepage stability of terminal moraine ridge dam. The leading role of seepage deformation in some glacial lake outburst mechanism is proposed and proved.