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排序方式: 共有238条查询结果,搜索用时 31 毫秒
111.
112.
利用FLAC模拟了两个不同直径圆形隧洞的剪切应变局部化过程。为了模拟隧洞开挖,利用编写的FISH函数删除隧洞内部的单元。岩石服从莫尔库仑剪破坏与拉破坏复合的破坏准则,破坏之后呈现应变软化-理想塑性行为。本文的模拟分为3步:首先,将静水压力施加在模型上,直至达到静力平衡状态;然后,利用编写的FISH函数,开挖隧洞;最后,计算重新开始,直至达到静力平衡状态(对于小孔隧洞)或者塑性流动状态(对于大孔隧洞)。模拟结果表明,多个“狗耳”形或V形坑在小孔隧洞周边附近产生,最终,围岩处于平衡状态。这一结果与陆家佑和王昌明(1994)的实验结果及许多现场观察结果一致。对于大孔隧洞,由于在围岩中出现了多条剪切带,因而隧洞的整个断面均遭到了破坏。这一现象与现场观察到的猛烈破坏现象类似。隧洞的剪切应变局部化受隧洞尺寸的影响。 相似文献
113.
依托毗邻深圳水库的深圳东部过境高速公路连接线工程,研制了以控制渗透系数为核心的围岩-支护体系新型相似材料,利用自制渗流模型试验系统,研究不同高度的动、静作用水头对水压力、排水量及渗流场的影响。试验表明:地下水位较高时,注浆圈内壁经历块状润湿、浸润线状态、完全湿润、拱腰以上挂满水珠、间断性水流线等过程,而随着作用水头的降低,渗流速度减慢,渗流时间大幅增加;随着静水头高度降低,各特征点水压力呈近似线性下降,且作用水头越小,相同位置二衬和注浆圈背后的水压力值更加接近,而隧道排水量测试的离散性也越小;动水头作用下,水压力随时间变化有明显的滞后性,其时间效应不利于结构稳定,而动水头下降过程中浅埋处更易受到影响,需加强隧道顶部的承载及抗渗设计,隧道排水量值随动水头下降呈减小的趋势,且降低相同水位差所需的时间越长。 相似文献
114.
重力和构造力在地壳中的作用 总被引:18,自引:1,他引:18
本文对于“上覆岩石重力数值等同于静水压力数值”的认识提出了新的看法,地壳中应力场T可以看成是一个静水压力P和一个差应力σ的复合、则静水压力P是由重力附加静水压力PR和构造力附加静水压力PS两者叠合而成,而不仅仅是来自上覆岩石的总重量,有限元模型计算表明,在同样外力条件下,从挤压变形带,剪切变形带到引张变形带中的各带构造附加静水压力值呈降低变化,即PC〉PZh〉Pt,因而构造附加静水压力得造成局部静 相似文献
115.
铝类絮凝剂对细颗粒泥沙絮凝沉降有重要作用,常应用于浑水澄清、农业污水处理等研究中。在AlCl3浓度为0~1.7mmol/L,泥沙浓度为10g/L时,用吸管法研究了AlCl3对细颗粒泥沙絮凝沉降的影响,结果表明:在液面下同一深度,泥沙浓度随时间呈指数衰减;悬液经多次搅拌后再沉降,其沉速减缓;当AlCl3浓度为0.9~1.7mmol/L时,出现明显的清浑水交界面,交界面随时间等速下降,平均沉速为4.756cm/min,对应的絮团平均粒径为0.0315mm;土娄土絮凝临界粒径为0.027mm。 相似文献
116.
通过把比降测量的观测成果进行科学的分析 ,得出泥沙淤积的原因 ,并提出了有关的航道测量、整治工程的一些建议 相似文献
117.
从GPS推算大气水汽的误差分析 总被引:7,自引:0,他引:7
讨论了从GPS观测数据推算大气水汽值的各种误差,分析了这些误差对大气水汽值的影响。 相似文献
118.
Hydrodynamic behaviour of Taupo 1800a pumice: implications for the sedimentology of remobilized pyroclasts 总被引:1,自引:0,他引:1
Abstract Large‐scale explosive eruptions from silicic caldera volcanoes can generate huge volumes of pyroclastic material in terrestrial and marine environments. On land, erosion, remobilization and redeposition of this debris is predominantly carried out by running water in the form of precipitation run‐off. Conversely, in the submarine realm, both primary emplacement and subsequent remobilization are influenced by the presence of water as a transporting medium. Despite this, and the number of studies devoted to volcaniclastic sedimentation, relatively little attention has been paid to the hydrodynamic behaviour of the particles themselves, which ought to underpin any assessment of transport or depositional process. This is crucial, as many volcanic particles exhibit variable density: according to composition and as functions of differing degrees of vesiculation and the extent to which pore space is filled by water and/or gaseous phases during transport and deposition. Investigation of the physical and hydrodynamic properties of Taupo 1800a pumice, with reference to sedimentary facies developed during the eruption aftermath, shows that, although buoyant when dry, when sufficiently waterlogged, cool pumice clasts will sink and behave more like quartzo‐feldspathic material. Saturation is apparently achieved by a combination of rapid capillary flooding of large interconnected vesicles and slower diffusional air–water exchange in smaller pores. Low saturated pumice densities result in lower settling velocities and easier entrainment by tractional currents than those for equivalent‐sized quartzo‐feldspathic or crystal/lithic particles. Fine‐grained pumice is conversely harder to entrain because of the frictional interlocking of angular particles. These unusual properties of temporary buoyancy, variable saturation, low density and size‐dependent cohesion complicate interpretations of the depositional setting and energy of pumiceous sediments and give rise to several unique facies. These findings have implications not only for the analysis of remobilized pyroclastic facies in terrestrial and marine environments, but also for primary depositional processes during subaqueous explosive volcanism. 相似文献
119.
Lü Guxian 《中国地质大学学报(英文版)》2004,15(2):145-151
Some current methods for the calculation of the geogenetic depth are based on the hydrostatic model, it is induced that the depth in certain underground place is equal to the pressure divided by the specific weight of rock, on the assumption that the rock is hydrostatic and overlain by no other force but gravity. However, most of rock is in a deformation environment and non-hydrostatic state, especially in an orogenic belt, so that the calculated depth may be exaggerated in comparison with the actual depth according to the hydrostatic formula. In the finite slight deformation and elastic model, the relative actual depth value from the 3-axis strain data was obtained with the measurement of strain including that of superimposed tectonic forces but excluding that of time factor for the strain. If some data on the strain speed are obtained, the depth would be more realistically calculated according to the rheologicai model because the geological body often experiences long-term creep strains. 相似文献
120.
Effects of Tectonic Force on Hydrostatic Pressure in Crust 总被引:1,自引:0,他引:1
Lü Guxian 《中国地质大学学报(英文版)》2004,15(2):155-161
The research into the hydrostatic pressure in the crust has been previously conducted from the viewpoint that the hydrostatic pressure is equal to the gravity, based on the fact that the hydrostatic pressure is derived mainly from the gravity of its overlying rocks. In this paper, the stress state of any point in the crust is suggested to have been caused by both the gravity and the tectonic force. The author proposes that the hydrostatic pressure is a combination or superposition of two isotropic stresses in the tectonic force and gravity stress fields. The results obtained with a finite-element simulation indicate that the additional hydrostatic pressure borne by rocks decreases gradually from the compression zone (pc^s),the shear zone (psh^s) to the tensile zone (pt^s), and that the difference in the additional tectonic hydrostatic pressure between these deformed zones tends to increase, following the increase in the absolute value and/or the difference in external forces between different directions. This paper presents the foundation for the research into the tectonic physicochemistry. 相似文献