深基坑双排桩支护结构上的变形和土压力研究   总被引：7，自引：0，他引：7  

聂庆科  胡建敏  吴刚 《岩土力学》2008,29(11):3089-3094

根据某大型深基坑工程的实测资料,对双排桩支护结构上的截面弯矩、变形和土压力分布特征进行了研究,并对基坑开挖的空间效应、冠梁刚度对土压力的影响、支护结构变形与土压力分布的关系、双排桩支护结构与土的相互作用机制等进行分析。研究表明,深基坑双排桩支护结构上的土压力分布是十分复杂的,用传统的土压力计算方法估算双排桩支护结构上的土压力存在较大偏差。其研究结果为双排桩支护结构上土压力设计计算模式的建立提供了依据。  相似文献   

清江水布垭库区大堰塘滑坡涌浪分析   总被引：4，自引：0，他引：4  

殷坤龙  杜娟  汪洋 《岩土力学》2008,29(12):3266-3270

2007年6月15日位于水布垭水库巴东县清太平镇的大堰塘滑坡发生滑动,激起高达50 m的巨大涌浪,造成了沿岸的人员伤亡。为了解决大堰塘滑坡引起的涌浪问题,把滑坡引起的涌浪分为体积涌浪和冲击涌浪两部分。根据体积守恒原理及块体水下运动的位移公式求出了初始涌浪的计算公式。把滑坡涌浪衰减过程分为急剧衰减和缓慢衰减两个阶段来考虑,并认为急剧衰减阶段的涌浪的衰减符合指数衰减规律,缓慢衰减阶段符合明槽水流的沿程水头损失规律,对其涌浪的传播和爬坡进行了深入探讨,并与实际调查结果进行了对比分析,该成果对水库库岸滑坡的涌浪传播的研究具有一定的参考意义。  相似文献   

岩层阻水性能及自然导升高度研究   总被引：2，自引：1，他引：1  

尹尚先  虎维岳 《煤田地质与勘探》2008,36(1):34-36,40

在沉积、成岩或者构造运动过程中,由于含水层内超压流体引起围岩爆裂导致流体在弱渗透层或者隔水层中导升,形成含水层的自然导升带。影响岩层阻水性能以及导升高度的因素有:构造、地应力、岩层渗透性和力学特性及其物理化学性质、水压力等。实验表明:初始水头压力越大,水头衰减速率就越大;水头压力损耗随着介质的渗透系数增大而减小。实际观测表明:泥岩、粉砂岩、中砂岩、灰岩的阻水性能由大到小,而导升高度则由小变大。通过实验和实际观测总结出流体3种导升机制:局部关键层整体破断裂缝、欠压实带中的壳破裂裂缝和水力压裂裂缝。   相似文献   

基于Duncan-Chang本构的非线性土压力模型     

吴明  夏唐代  俞峰 《煤田地质与勘探》2008,36(2):36-39

假设基坑工程中挡土结构的变形和土压力服从双曲线模型,类比Duncan-Chang本构建模思想,在前人关于基坑主动区和被动区变形假设的基础上,建立了可以考虑位移变化的非线性土压力模型。把非线性土压力模型和Duncan-Chang本构模型联系起来,使得本文非线性土压力模型参数确定有根据。把弹性地基梁模型和该非线性土压力联系起来,使得弹性抗力系数的概念更加明确。以m法为例,深入分析了m法的影响因素。   相似文献   

差应力与石英组构关系的实验研究     

马瑞  田海民  张刚 《吉林大学学报(地球科学版)》2009,39(1):89

为了探讨柯石英的形成条件,利用河北省平山县西柏坡地区太古代阜平群中的黑云母片麻岩进行高温高压条件下的岩石变形实验。实验的温度为800 ℃,围压为0.2 GPa,应变量为10%,应变速率为10^-5/s。实验结果表明,变形后样品中不同部位石英颗粒的激光拉曼光谱与标准的石英光谱相比较发生了明显的变化,具体表现为：挤压带中,石英颗粒的光谱出现了9个峰,而标准石英光谱为6个峰;在剪切带中,石英颗粒的谱线只有一个清晰的峰,在拉伸带中,石英颗粒的谱线无论峰的数目还是出现的位置都与标准石英光谱有着显著的区别,说明导致岩石变形的差应力对石英晶格结构的改造具有一定的影响。  相似文献   

深水连续刚构桥地震响应分析   总被引：2，自引：0，他引：2  

刘振宇  李乔  赵灿晖  蒋劲松 《地震工程与工程振动》2009,29(4)

本文探讨连续刚构桥在深水中地震响应的特性.首先建立了地震作用下深水桥梁的运动方程,简要阐述了该运动方程的求解方法,应用该运动方程,对一座桥墩淹没水深168m的连续刚构桥进行了地震响应分析,考察了在纵向、横向激励作用下桥墩的内力响应和位移响应特征,探讨了矩形空心截面桥墩内域水、外域水对桥墩地震响应的影响,结果表明,由于墩-水相互作用,桥墩的位移和内力响应均有明显增大,对于矩形空心墩,内域水和外域水的影响应同时计入.  相似文献   

Phreatomagmatic volcanic hazards where rift-systems meet the sea, a study from Ambae Island, Vanuatu   总被引：1，自引：0，他引：1  

Kroly Nmeth  Shane J. Cronin 《Journal of Volcanology and Geothermal Research》2009,180(2-4):246

Ambae Island is a mafic stratovolcano located in the northern Vanuatu volcanic arc and has a NE–SW rift-controlled elongated shape. Several hundred scoria cones and fissure-fed lava fields occur along its long axis. After many decades of quiescence, Ambae Island erupted on the 28th of November 2005, disrupting the lives of its 10,000 inhabitants. Its activity remained focused at the central (crater-lake filled) vent and this is where hazard-assessments were focused. These assessments initially neglected that maars, tephra cones and rings occur at each tip of the island where the eruptive activity occurred < 500 and < 300 yr B.P. The products of this explosive phreatomagmatic activity are located where the rift axis meets the sea. At the NE edge of the island five tephra rings occur, each comparable in size to those on the summit of Ambae. Along the NE coastline, a near-continuous cliff section exposes an up to 25 m thick succession of near-vent phreatomagmatic tephra units derived from closely spaced vents. This can be subdivided into two major lithofacies associations. The first association represents when the locus of explosions was below sea level and comprises matrix-supported, massive to weakly stratified beds of coarse ash and lapilli. These are dominant in the lowermost part of the sequence and commonly contain coral fragments, indicating that the loci of explosion were located within a reef or coral sediment near the syn-eruptive shoreline. The second type indicate more stable vent conditions and rapidly repeating explosions of high intensity, producing fine-grained tephra with undulatory bedding and cross-lamination as well as megaripple bedforms. These surge and fall beds are more common in the uppermost part of the succession and form a few-m-thick pile. An older tephra succession of similar character occurs below, and buried trees in growth position, as well as those flattened within base surge beds. This implies that the centre of this eruption was very near the coastline. The processes implied by these deposits are amongst the most violent forms of volcanism on this island. In addition, the lowland and coastal areas affected by these events are the most heavily populated. This circumstance is mirrored on many similar volcanic islands, including the nearby SW Pacific examples of Taveuni (Fiji), Upolu and Savai'i (Samoa), and Ambrym (Vanuatu). These locations are paradoxically often considered safe areas during summit/central-vent eruptions, simply because they are farthest from the central sources of ash-fall and lahar hazard. The observations presented here necessitate a revision of this view.  相似文献   

The architecture, eruptive history, and evolution of the Table Rock Complex, Oregon: From a Surtseyan to an energetic maar eruption     

Brittany D. Brand  Amanda B. Clarke   《Journal of Volcanology and Geothermal Research》2009,180(2-4):203

The Table Rock Complex (TRC; Pliocene–Pleistocene), first documented and described by Heiken [Heiken, G.H., 1971. Tuff rings; examples from the Fort Rock-Christmas Lake valley basin, south-central Oregon. J. Geophy. Res. 76, 5615-5626.], is a large and well-exposed mafic phreatomagmatic complex in the Fort Rock–Christmas Lake Valley Basin, south-central Oregon. It spans an area of approximately 40 km², and consists of a large tuff cone in the south (TRC1), and a large tuff ring in the northeast (TRC2). At least seven additional, smaller explosion craters were formed along the flanks of the complex in the time between the two main eruptions. The first period of activity, TRC1, initiated with a Surtseyan-style eruption through a 60–70 m deep lake. The TRC1 deposits are dominated by multiple, 1-2 m thick, fining upward sequences of massive to diffusely-stratified lapilli tuff with intermittent zones of reverse grading, followed by a finely-laminated cap of fine-grained sediment. The massive deposits are interpreted as the result of eruption-fed, subaqueous turbidity current deposits; whereas, the finely laminated cap likely resulted from fallout of suspended fine-grained material through a water column. Other common features are erosive channel scour-and-fill deposits, massive tuff breccias, and abundant soft sediment deformation due to rapid sediment loading. Subaerial TRC1 deposits are exposed only proximal to the edifice, and consist of cross-stratified base-surge deposits. The eruption built a large tuff cone above the lake surface ending with an effusive stage, which produced a lava lake in the crater (365 m above the lake floor). A significant repose period occurred between the TRC1 and TRC2 eruptions, evidenced by up to 50 cm of diatomitic lake sediments at the contact between the two tuff sequences. The TRC2 eruption was the last and most energetic in the complex. General edifice morphology and a high percentage of accidental material suggest eruption through saturated TRC1 deposits and/or playa lake sediments. TRC2 deposits are dominated by three-dimensional dune features with wavelengths 200–500 m perpendicular to the flow, and 20–200 m parallel to the direction of flow depending on distance from source. Large U-shaped channels (10–32 m deep), run-up features over obstacles tens of meters high, and a large (13 m) chute-and-pool feature are also identified. The TRC2 deposits are interpreted as the products of multiple, erosive, highly-inflated pyroclastic surges resulting from collapse of an unusually high eruption column relative to previously documented mafic phreatomagmatic eruptions.  相似文献   

Lattice-Boltzmann simulations of the capillary pressure–saturation–interfacial area relationship for porous media     

Mark L. Porter  Marcel G. Schaap  Dorthe Wildenschild 《Advances in water resources》2009,32(11):1632-1640

Hysteresis in the relationship between capillary pressure (P_c), wetting phase saturation (S_w) and nonwetting–wetting interfacial area per volume (a_nw) is investigated using multiphase lattice-Boltzmann simulations of drainage and imbibition in a glass bead porous system. In order to validate the simulations, the P_c–S_w and a_nw–S_w main hysteresis loops were compared to experimental data reported by Culligan et al. [Culligan KA, Wildenschild D, Christensen BS, Gray WG, Rivers ML, Tompson AB. Interfacial area measurements for unsaturated flow through porous media. Water Resour Res 2004;40:W12413]. In general, the comparison shows that the simulations are reliable and capture the important physical processes in the experimental system. P_c–S_w curves, a_nw–S_w curves and phase distributions (within the pores) show good agreement during drainage, but less satisfactory agreement during imbibition. Drainage and imbibition scanning curves were simulated in order to construct P_c–S_w–a_nw surfaces. The root mean squared error (RMSE) and mean absolute error (MAE) between drainage and imbibition surfaces was 0.10 mm⁻¹ and 0.03 mm⁻¹, respectively. This small difference indicates that hysteresis is virtually nonexistent in the P_c–S_w–a_nw relationship for the multiphase system studied here. Additionally, a surface was fit to the main loop (excluding scanning curves) of the drainage and imbibition P_c–S_w–a_nw data and compared to the surface fit to all of the data. The differences between these two surfaces were small (RMSE = 0.05 mm⁻¹ and MAE = 0.01 mm⁻¹) indicating that the P_c–S_w–a_nw surface is adequately represented without the need for the scanning curve data, which greatly reduces the amount of data required to construct the non-hysteretic P_c–S_w–a_nw surface for this data.  相似文献   

Pressure-resistant instruments     

G. S. Predtechenskii 《Seismic Instruments》2009,45(1):19-20

Prospects of using case-free pressure-resistant instruments for geophysical work and marine research are briefly considered.  相似文献