海堤施工中软土地基沉降计算分析     

孟光青  程鹏 《岩土工程技术》2012,26(4):208-211

从剖析沉降固结的概念,探讨常规沉降计算公式的适用性出发,对照海堤工程实践中暴露出来的问题,指出软基筑堤工程实践中沉降计算分析的注意事项和建议,以起到抛砖引玉的效果。  相似文献   

山东诸城早白垩世莱阳期古地震事件与恐龙迁移   总被引：1，自引：0，他引：1  

何碧竹  乔秀夫  田洪水  张艳霞 《地质学报》2012,86(8):1320-1330

在诸城断陷皇华镇大山村黄龙沟存在丰富的、多样的恐龙足迹化石,在紧邻化石埋藏层下伏及上覆地层中发现了下白垩统莱阳群杨庄组多套古地震记录,主要包含波状褶皱、底劈构造、液化砂岩脉、液化角砾岩、粒序断层、卷曲变形和震积不整合等塑性、脆性软沉积物变形构造。分析表明初始沉积物、沉积相及构造作用确定了地震活动作用时形成的软沉积物变形构造类型。在早白垩世莱阳群沉积中期,地震活动具有阶段性及频发性,以单向挤压的丘-槽构造及双向挤压的波状变形为主,且后期有构造活动强度加大的特征。根据已识别的古地震记录发育及古地震活动强度分析,推测此时期发震断裂可能是断陷的南缘断裂——五莲断裂。区域构造作用使得该时期沉积环境发生变化,由湖相逐渐过渡到河流相,在突发古地震事件发生之后,在滨浅湖区域留下了丰富的恐龙迁徙足迹。古地震记录的研究,可建立古地震事件与沉积、构造演化的联系,约束构造作用的属性、频次及时限,为确定盆地及周缘构造-沉积演化历史提供证据。  相似文献   

反倾层状边坡弯曲折断的应力及挠度判据   总被引：9，自引：6，他引：3  

陈红旗  黄润秋 《工程地质学报》2004,12(3):243-246

以地质分析为基础 ,将反倾层状边坡的任意岩层概化为受复合作用力的板梁模型 ,通过简单的力学解析 ,开展了反倾层状岩石边坡弯曲折断判据的研究。依据岩层折断时和相临岩层的瞬时关系 ,将岩层下部视为瞬时临空状态 ,考虑岩层自重荷载和上部岩层附加荷载 (上部岩层重力荷载、层间摩擦力 )的共同作用 ,基于最大拉应力准则 ,提出了岩层弯曲折断的应力判据 ;依据应力判据 ,得到了岩层弯曲折断的挠度判据 ;利用应力判据及挠度判据 ,可实现反倾层状边坡弯曲折断的现场判定及其控制设计  相似文献   

汶川8.0级地震前后陕西地区地倾斜特征迁移分析     

张创军  牛安福 《大地测量与地球动力学》2009,29(Z1):11-14

对汶川8.0级地震前后陕西地区地倾斜观测资料的分析发现，汶川地震前陕西地区地倾斜存在沿龙门山断裂带方向由东北向西南震中迁移，震后地倾斜反向迁移，迁移平均速度为3～4 km/天。进一步分析认为，震前陕西地区地倾斜向震源迁移可能对汶川8.0级地震起到了触发作用，而震后地倾斜向远场迁移有可能是诱发陕甘川交界的中强余震的主因。  相似文献   

北京及周边地区雷暴阵风锋特征统计分析     

何娜  丁青兰  俞小鼎  付宗钰  周璇  刘璐  李桑  柳克 《气象学报》2020,78(2):250-259

为全面和系统研究北京及周边地区阵风锋各方面特征,使用2006—2015年暖季（5—9月）北京多普勒雷达探测资料及北京、河北、天津自动气象站观测资料对北京及周边地区的阵风锋过程进行综合统计分析。结果表明,346次阵风锋过程有232次触发了对流,占总数的67%,表明阵风锋对雷暴具有较强的抬升触发能力。阵风锋在6—8月出现的日数占5—9月阵风锋总日数的85%;出现的时段主要是午后至傍晚（12—21时,北京时）,维持时间0.5—3 h;阵风锋在北京东南方向生成的数量最多,且触发对流的次数也最多;其次为偏东和东北方向;偏南和西南方向生成阵风锋数量居中,而偏北、偏西和西北地区阵风锋个例相对较少,触发对流的比例也相对较低。产生阵风锋的母风暴中48%为孤立雷暴（包括孤立多单体和超级单体风暴）,31%为雷暴群,21%为飑线;97%的母风暴最强回波在50 dBz以上,阵风锋的回波强度为10—25 dBz。91%的阵风锋移动速度集中在10—60 km/h,84%的阵风锋与母风暴的最大距离为1—60 km;在母风暴回波强度减弱到30 dBz以下时,80%的阵风锋能够继续维持的时间不超过2 h。阵风锋母风暴向东南方向移动的个例最多,从阵风锋和母风暴移动方向的关系来看,阵风锋与母风暴移向一致的情况占比最高,为32%,其次为母风暴无移动及阵风锋弧形扩散情况,各占17%;阵风锋与母风暴移向相反情况所占比例最低,只有3%。最后统计了阵风锋经过地面自动气象站时,自动观测量的变化情况。结果显示,阵风锋在经过地面自动气象站时会造成风速增大、温度降低、相对湿度增大、气压升高。   相似文献   

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张华  蒋海昆  姚宏  周斌  郭培兰  阎春恒  文翔 《大地测量与地球动力学》2014,34(4):88-91

2013-06~07??????????3?????????????С??????????п???????У???????????????????????????????????????????????????????????????????????????????????????????????????????????(ETAS???)??????????????????????崥???????????????й???????????????????  相似文献   

泥石流源区典型草本植物根系抗拉试验   总被引：5，自引：0，他引：5  

陆桂红  欧国强  杨顺  王钧  宇岩 《山地学报》2014,32(6)

植被对于泥石流源区的生态修复和物源稳定具有重要意义,其中植物根系的抗拉力学特性是影响植物护坡的主要因素之一。为了探究泥石流源区植物根系的抗拉特性,以都江堰市锅圈岩泥石流源区为研究区,在野外调查的基础上,通过重要值计算确定了源区典型草本植物并进行抗拉强度试验。研究表明,锅圈岩泥石流源区主要分布有寒芒、节节草等对恶劣环境适应性强的乡土植物,它们的根系平均分布深度在30 cm以内;根系抗拉力与根径呈幂函数正相关关系,抗拉力随根径的增大而增大。当根径0.50 mm时,抗拉强度与根径也表现出幂函数关系;当根径0.50 mm时,部分植物根系的抗拉强度值波动较大。不同植物根系的平均抗拉强度从大到小依次为铁杆蒿(106.24 MPa)、节节草(非节点处,30.79 MPa)、草地早熟禾(28.69 MPa)、小飞蓬(20.20 MPa)、多头苦荬(18.77 MPa)、寒芒(老根,14.87 MPa)、节节草(节点处,12.67 MPa)、寒芒(新根,8.29 MPa)。泥石流源区草本植物的根系抗拉力学特性良好,对稳固浅层土体和泥石流物源有积极作用。  相似文献   

Evolution of the stress and strain fields in the Eastern Cordillera,Colombia     

《Journal of Structural Geology》2014

This work integrates stress data from Global Positioning System measurements and earthquake focal mechanism solutions, with new borehole breakout and natural fracture system data to better understand the complex interactions between the major tectonic plates in northwestern South America and to examine how the stress regime in the Eastern Cordillera and the Llanos foothills in Colombia has evolved through time. The dataset was used to generate an integrated stress map of the northern Andes and to propose a model for stress evolution in the Eastern Cordillera. In the Cordillera, the primary present-day maximum principal stress direction is WNW–ESE to NW–SE, and is in the direction of maximum shortening in the mountain range. There is also a secondary maximum principal stress direction that is E–W to ENE–WSW, which is associated with the northeastward “escape” of the North Andean block, relative to stable South America. In the Cupiagua hydrocarbon field, located in the Llanos foothills, the dominant NNE–SSW fractures are produced by the Panama arc–North Andes collision and range-normal compression. However, less well developed asymmetrical fractures oriented E–W to WSW–ENE and NNW–SSE are also present, and may be related to pre-folding stresses in the foreland basin of the Central Cordillera or to present-day shear associated with the northeastward “escape” of the north Andean block. Our study results suggest that an important driver for orogenic deformation and changes in the stress field at obliquely convergent subduction zone boundaries is the arrival of thickened crust, such as island arcs and aseismic ridges, at the trench.  相似文献   

Slip line theory applied to a retaining wall–unsaturated soil interaction problem     

《Computers and Geotechnics》2014

An extension of slip line theory to unsaturated soils is presented and applied to the problem of a rigid retaining wall rotating about its toe into unsaturated soils. Suction is introduced using the effective stress concept. Soil–wall interface friction is defined carefully. The influence of suction on limiting passive earth pressures is analysed for two soils under steady state evaporation and infiltration. Suction increases the limiting passive stress at the soil–wall interface, with a dependence on the steady state flow type. The displacement of the retained soil is studied assuming the wall undergoes a rotation increment. The results show a clear difference in the displacement for evaporation and infiltration.  相似文献   

Test and numerical research on wall deflections induced by pre-excavation dewatering     

《Computers and Geotechnics》2014

Numerous studies have been devoted to the performance of excavations and adjacent facilities. In contrast, few studies have focused on retaining wall deflections induced by pre-excavation dewatering. However, considerable inward cantilever deflections were observed for a diaphragm wall in a pre-excavation dewatering test based on a long and narrow metro excavation, and the maximum deflection reached 10 mm (37.6% of the allowable wall deflection for the project). Based on the test results, a three-dimensional soil–fluid coupled finite element model was established and used to study the mechanism of the dewatering-induced diaphragm wall deflections. Numerical results indicated that the diaphragm wall deflection results from three factors: (1) the seepage force around the dewatering well and the soil–wall interaction caused the inward horizontal displacement of the soil inside the excavation; (2) the reduced total earth pressure on the excavated side of the diaphragm wall above approximately 1/2 of the maximum dewatering depth disequilibrated the original earth pressure on both sides of the diaphragm wall; and (3) the different negative friction on the excavated and retained sides of the diaphragm wall led to the rotation of the diaphragm wall into the excavation.  相似文献