桩基变形分析及水平静载试验探讨

本文通过对拟建风电场项目的3根桩长10m,桩身直径为800mm的机械钻孔混凝土灌注桩试验桩进行单桩水平静载试验,准确测定出该工程的试验桩7#、8#、9#三根单桩水平承载力特征值不小于60KN,7#单桩的桩顶水平最大位移量为3.73mm、8#单桩的桩顶水平最大位移量为2.38mm、9#单桩的桩顶水平最大位移量为1.36mm。为项目下一步的设计提供了依据。     

抗滑桩试验研究

抗滑桩,作为滑坡防治的一项工程措施,它较为优越,现已得到普遍采用。 然而目前抗滑桩的设计与计算方法尚不一致,也不完善。其中最大的分歧是,抗滑桩在受力条件或计算力学模式方面,是否与普通地基中的侧向受荷桩完全相同;或者     

软岩高边坡预应力锚索抗滑桩的设计计算

目前已提出了多种预应力错索抗滑桩的设计计算方法,例如按Winkler弹怀地基梁的方法、错索与桩的协调变形的方法等.由于软弱岩体的变形特征,结构与岩体的相互作用机理较为复杂,这些方法难以直接应用于软岩高边坡工程,需要加以分析改进.应该分析预应力锚索抗滑桩的施工顺序、实际受力条件、锚索预应力的主要控制因素等,分阶段进行计算,这样得出的计算结果才有可能与实际情况一致.在充分吸取现有计算方法优点的基础上,提出了改进的方法.通过实际工程的计算,得出了较为符合实际情况的结果.     

三峡库岸城区滑坡治理与沿江公路建设一体化模式--以重庆万州清泉路滑坡为例

三峡库岸城区滑坡90%属于由第四纪松散土体组成的散体滑坡,滑坡区属于城区重要组成部分,降雨及三峡库水位降落是此类滑坡孕发的动力因素。本文以重庆万州清泉路滑坡为例,基于库岸城区滑坡防治原则,构建了实用的滑坡治理与沿江路建设一体化模式,推导了抗滑桩的内力计算方法;详细分析了一体化模式的结构组成及受力特性。研究成果对于三峡库区城区滑坡的治理与开发利用具有较强的指导借鉴作用。     

广州岩溶地区岩石地基承载力分析

岩溶地质条件下岩石地基的受力性状比普通地质条件下要复杂得多,岩石地基的承载力与桩身周围溶洞的大小、分布、溶洞个数、桩端持力层情况等因素有着密切关系。本文结合工程实例,将根据岩基荷载实验法、岩石室内饱和单轴抗压强度计算法分析地基承载力。     

水泥土搅拌桩和袋装砂井联合法在填方边坡软基处理中的应用

通过填方边坡下覆软弱地基处理采用水泥土搅拌桩和袋装砂井联合法进行处理的案例得出填方边坡软基处理效果较好,地基土体强度可以迅速提高,同时经过水泥土搅拌桩处理填方边坡的地基,能够使得高填方边坡的地基的稳定性大大提高。     

圆形抗滑桩在滑坡治理中的应用研究

滑坡治理是个综合治理的过程,应根据滑坡类型、规模、稳定性,结合滑坡区工程地质条件、建筑类型及分布情况、施工设备和施工季节等条件,选用多种形式综合治理,目的是将各种整治措施组合成为最有效的工程措施,降低整治滑坡的工程造价。在各种滑坡的治理中,方形抗滑桩由于强大的抗弯性能和抗剪性能使用最多,圆形抗滑桩使用较少。在特殊条件下,可以采用圆形桩的支护方式。通过在广东某个工程中的试验研究,发现圆形抗滑桩也能较好的应用。     

CFG桩施工中使用长螺旋钻存在问题的刨析

通过工程实例,介绍了长螺旋钻孔在CFG桩施工中存在的由于钻门打不开而造成堵管或爆管,憋钻和卡钻,断桩、缩径和桩身缺陷等事故及采取的防治措施。     

磨刀溪岩石滑坡分析与治理

磨刀溪岩石滑坡由于人工开挖、在支挡不当的情况下产生并逐步扩大。对此,着重采用了工程地质力学法对该滑坡进行了分析,明确了该滑坡为一切层滑坡,其发生发展与岩层的结构面关系密切。在此基础上以推力传递系数法及地基系数等为理论,确定以一排抗滑桩及一排锚索抗滑桩进行支挡,并在下排桩前采用锚索框架对桩前岩土体进行加固,以确保抗滑桩的锚固段不松弛变形,同时结合疏排水的措施对该滑坡予以彻底治理,从实践看最后一次的治理取得了成功。同时分析了前面几次失败的治理经历,从中总结了很多有益的经验和教训,并从治理实践中证明了该滑坡治理措施的合理性和有效性,值得同类工程借鉴。     

佛山市顺德区飞鹅山Ⅲ号滑坡形成机理与防治技术

采用工程地质钻探、物探、地质测绘及室内试验等技术方法探讨飞鹅山Ⅲ号滑坡形成机理与防治技术。结果表明：1）滑坡体主要岩性为泥质粉砂岩,飞鹅山滑坡属于新形成的深层中型牵引式滑坡,在平面上呈圈椅状。2）滑坡属于双层滑面滑坡,主滑面以中型深层滑坡为主,主滑体上部发育中型中厚层滑坡。3）滑坡产生的原因为：(1)泥质粉砂岩倾向与坡向基本一致,且岩层倾角为中等倾角;(2)人工开挖使坡脚形成高陡临空面,抗滑力大为降低;(3)雨水沿层面及节理裂隙入渗至坡体深部,大大增加岩土体容重,同时泥质粉砂岩遇水软化,抗剪强度显著降低。4）结合该滑坡区地质环境条件,采用坡面削坡+锚杆（索）+格构梁+双排预应力锚拉抗滑桩+三维网植草绿化+截排水+毛石挡墙的综合治理方法进行防治,监测结果显示该滑坡变形及位移已得到有效控制,整治效果良好。     

Ecological and population changes in fishing communities of the North Atlantic Arc

In the decades since World War II, large-scale ecological changes have affected fishing communities across the northern Atlantic. Substantial declines hit their historically important resources, most notably the Atlantic cod. Such declines were often accompanied by increases in other, previously less exploited, species. Interactions between fishing pressure and environmental variation have driven ecological change. Ecological changes in turn reshaped the fisheries, contributing to altered demographic profiles of fisheries-dependent communities. Many places lost population, especially through out-migration of young adults. Broad social forces also contributed to these trends, but the timing and geographical details of population changes often correspond to specific fisheries/ecological events.     

Double-planed deep seismic zone and upper-mantle structure in the Northeastern Japan Arc

Summary. The ScSp wave converted from the ScS wave at the boundary between the descending lithospheric slab and the mantle above it was clearly observed from a nearby deep earthquake with magnitude 7.7 at some stations of the seismic network of Tohoku University which covers the Tohoku District, the northeastern part of Honshu, Japan. By applying the three-dimensional seismic-ray tracing method, the location of this boundary was determined from the difference in arrival time between the ScS and ScSp waves. The result shows that the upper boundary of the descending slab lies exactly on the upper plane of the double-planed deep seismic zone found in the Northeastern Japan Arc.
There is an additional evidence that the boundary is located on the upper plane of the double-planed deep seismic zone. The hypocentre distribution of intermediate-depth earthquakes located by the small-scale seismic-array observation is extremely different from that obtained by the relatively large-scale seismic network. The discrepancy in the distribution of hypocentres of the same earthquake independently located is well explained by the inclined lithospheric slab model derived from the difference in arrival time between the ScS and ScSp waves.
The earthquakes with reverse faulting or with down-dip compressional stresses occur at the upper boundary of the descending slab. Within the descending slab, the earthquakes with down-dip extensional stresses also occur in a very narrow zone from 30 to 40 km below the dipping boundary in the depth range from 50 to about 200 km, and these shocks form the lower plane of the double-planed deep seismic zone.     

Upper Mantle Velocity Structure Estimated From Ps-Converted Wave Beneath the North-Eastern Japan Arc

Summary. The upper boundary of the descending oceanic plate is located by using PS -waves (converted from P to S at the boundary) in the Tohoku District, the north-eastern part of Honshu, Japan. the observed PS-P time data are well explained by a two-layered oceanic plate model composed of a thin low-velocity upper layer whose thickness is less than 10 km and a thick high-velocity lower layer; the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle. the estimated location of the upper boundary is just above the upper seismic plane of the double-planed deep seismic zone. This result indicates that events in the upper seismic plane, at least in the depth range from 60 to 150 km, occur within the thin low-velocity layer on the surface of the oceanic plate.