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21.
TTI介质qP波数值模拟方法因为考虑了倾角因素,可以比VTI介质qP波数值模拟方法更加准确地描述各向异性介质中地震波场的传播规律.文中用拟声波方程对TTI介质中的地震波场进行了高阶有限差分数值模拟,在改进衰减函数分布方式后,通过坐标变换,利用改进的完全匹配层(perfectly matched layer,PML)边界控制方程对波场边界进行吸收处理,取得了良好的效果;然后分析了拟声波方程数值模拟中的稳定性问题,并对波场中的伪横波进行压制.通过对不同模型的数值模拟,验证了文中使用的TTI介质拟声波波动方程的稳定性以及所采用的PML边界控制方程的可靠性和适用性. 相似文献
22.
边坡危岩落石作为在山区工程建设中经常遇到的一种地质灾害,严重威胁着铁路等交通工程的施工与运营安全。在多种因素的影响下,落石运动轨迹具有随机概率分布的特征,其能量状态和冲击大小和落石的运动状态密切相关。真实描述落石的运动轨迹,从而求解其能量状态及冲击力是后续针对性制定防护措施的前提和主要参考依据。本文在系统总结国内外既有落石分析软件的基础上,引入基于正态分布的概率计算方法,改进了落石运动轨迹计算的实用模型,并据此编制了一套落石分析计算软件,在概率计算的基础上,提出了落石运动的两条最不利轨迹,并采用多种方法对最不利轨迹的落石冲击力进行了计算。本软件已在贵广铁路何屋特大桥危岩落石工点进行了成功应用,取得了良好的效果,可在后续工点中推广应用。 相似文献
23.
库岸边坡发生失稳破坏大多与库水变幅有关,为了有效指导岸坡设计和防治工作,本文以陕西镇安抽水蓄能电站上库区一边坡为研究对象,利用Rocscience Phase2有限元软件,基于瞬时流模拟库水快速升降时坡体内渗流-应力耦合场,并采用SSR自定义搜索功能对迎水坡和背水坡分别计算稳定性后发现：在水位升降速度不变的条件下,当水位上升时,背水坡的安全系数持续减小,而迎水坡的安全系数先减小后增大,但两侧坡体均未发生破坏;当水位下降时,背水坡安全系数同样持续减小,但未发生破坏,迎水坡的安全系数也在持续减小,但在水位下降19 m时骤减,最终破坏。在水位升降幅度不变的条件下,当升降速度变化时,背水坡安全系数基本没有变化;当水位上升速度增大时,迎水坡安全系数逐渐增大,当水位下降速度增大时,迎水坡安全系数逐渐减小。建议水库运营时,库水下降幅度不宜超过18m;若要满足发电量要求并确保边坡不会发生失稳破坏,可将正常蓄水位抬升12m后进行发电。 相似文献
24.
KOMOLVILAS Veerayut TANAPALUNGKORN Weeradetch LATCHAROTE Panon LIKITLERSUANG Suched 《山地科学学报》2021,12(10):2580-2596
On 28th July 2018, a massive landslide occurred in a mountainous area in Northern Thailand. The landslide after ten days of heavy rainfall generated the movement of uphill mountain soil into the populated village. This study presents a comprehensive failure analysis of local rainfall-induced landslides based on topographical and geological information. Rainfall measurement data were gathered from two rainfall stations close to the study area. The rainfall records show that the total monthly rainfalls in 2018 were significantly higher than the average monthly rainfalls over the past decade. Site investigation started with an unmanned aerial photogrammetric survey to generate a digital elevation model. Then, dynamic probing test, microtremor survey, and electrical resistivity survey were carried out along undisturbed soils beside the failed slope to evaluate the thickness of the soft soil cover on top of the rock basement. During the site survey, residual soil samples were collected to determine engineering properties in the laboratory. Finally, a slope stability analysis was performed to assess the landslide hazard based on the results of aerial photogrammetric survey, field exploration, and laboratory tests. The slope stability analysis and rainfall records revealed that the Huay Khab landslide was mainly caused by an increase in the water content of residual soils due to the prolonged rainfall which led to a sharp decrease in the shear strength. This leads to the conclusion that the proposed landslide investigation program could be used to assess the potential of landslide failure due to prolonged rainfall on a local scale. 相似文献
25.
As an important indicator of environmental and climate changes, snow chemical properties can be used to reflect microcosmic changes, large-scale environmental and climate changes. 174 groups of snow samples were collected from four different rivers, Jinta river, Sishui river, Binggou river, and Nancha river, in the eastern Qilian Mountains in west China from May 2014 to October 2017. The characteristics of inorganic ions, Ca~(2+), Mg~(2+), Na~+, K~+, Cl–, NO_3~–, HCO_3~–, and SO_2~–, in the samples were analyzed by Dionex-600 and Dionex-3000 ion chromatograph. The results show that Ca~(2+) is the main cation, while HCO_3~– is the main anion; the ion concentration of snow is higher than that of rain. After careful analysis, we draw the conclusion that due to the controlling of the westerly wind, the atmosphere of the Qilian Mountains is dry with high dust content in winter and spring, which makes the ions in the snow mainly derive from the weathering of carbonate rock and sulfate rock. The ions in snow cover mainly come from land-sourced dust, while less contribution is from marine sources and human activities. 相似文献
26.
The buckling failure of stratified rock slopes intersected by a set of steep discontinuities that are approximately parallel to the slope surface is frequently encountered while constructing railways and roadways in mountainous areas. In this study, an analytical approach based on the energy equilibrium principle is presented to solve the flexural buckling stability of stratified rock slopes within the framework of multilayer beam theory. The generalized HoekBrown failure criterion is introduced to reflect the influences of slope size(scale effects) on the buckling stability. Subsequently, numerical and physical modellings from previous literatures are employed to validate the proposed approach. Furthermore, a practical case of Bawang Mountain landslide is also used for the comparative analysis. The study shows that the present analytical approach is capable to provide a more reasonable assessment for the buckling failure of stratified rock slopes, compared with several existing analytical approaches. Finally, a detailed parametric study is implemented, and the results indicate that the effects of rock strength, rock deformation modulus, geological strength index, layer thickness and disturbance degree of rock mass on the buckling failure of stratified rock slopes are more significant than that of rock type and slope angle. 相似文献
27.
The mechanism that sustains the temporal stability of aboveground net primary production (ANPP) respond to nitrogen deposition is still controversial. Consequently, we investigated the mechanism of temporal stability of ANPP through the effect of N addition on diversity, species asynchrony and portfolio effects in northern Tibet alpine steppe over a period of three years. Our results showed that the community temporal stability did not significantly correlate with the species richness and Shannon-Wiener diversity. Species asynchrony and stability was also not significantly affected by N addition (p > 0.05). Furthermore, there was no significant relationship between species asynchrony and temporal stability. Although the value of portfolio effects (z) (z = 1.304, 95% confidence intervals: 1.029–1.597) was more than 1, the portfolio effects was not a primary driver of temporal stability due to the biodiversity being unaffected. The above results suggested that the richness, species asynchrony and portfolio effect could not support for mechanism of stability at the alpine steppe. From the results of path analysis, species temporal stability positively supports the community temporal stability in the alpine steppe ecosystem. According to the character of environment and vegetation of alpine steppe at North Tibet, we inferred that dominance species stability is more important than species richness for the community temporal stability. 相似文献
28.
An ancient landslide, situated in Deqin County, Yunnan Province, China, was used to investigate the reactivation by water infiltration. This study considers the infiltration process and landslide stability using finite-element method (FEM)-based models. The results show that the reactivation of old landslide deposit was triggered by the long-term leakage of diversion ditch before October 2012, and the reactivation was triggered again by the intense rainfall on 7–9 October 2012. The old cracks, which formed in the earlier reactivation of landslide, played a key role for the rainfall infiltration. They offered a preferential path for much more rainfall to infiltrate fast into deep soil, and caused wetting front to move down faster in landslide. The old slip zone with lower permeability was another important factor to cause the infiltrated water to accumulate and form a high pore water pressure above slip zone. Then the high pore water pressure decreased the shear strength of slip zone and triggered the reactivation of the old landslide deposit again. 相似文献
29.
SOKOŁOWSKA Justyna JÓZEFOWSKA Agnieszka WOŹNICA Karolina ZALESKI Tomasz 《山地科学学报》2019,14(7):1534-1545
The purpose of this research was to investigate the relationship between soil biota such as microbial activity, soil fauna (e.g., earthworms and enchytraeids), and soil physical and chemical properties. The study area was located in Pieniny National Park (PNP) in the Carpathian Mountains in southern Poland. Soil samples were collected from six forest monitoring areas of PNP from two soil layers (at 0–15 cm and 15–30 cm down, respectively). The investigated soils were classified to eutric cambisols and had silt or silt loam soil texture. Upon analysis, soil aggregate stability index was connected with other physical, chemical, and biological soil properties. It was noted that the stability index of 3 mm to 5 mm soil aggregates influenced pH and dissolved organic carbon. The stability index of 2 mm to 3 mm soil aggregates was positively correlated with dissolved organic carbon, soil moisture, microbial biomass carbon, total organic carbon, total nitrogen, and enchytraeid density, and negatively correlated with bulk density, particle density, porosity, and permanent wilting point. The stability index of 1 mm to 2 mm soil aggregates was positively correlated with total nitrogen, enchytraeid and earthworm density and negatively correlated with particle density, porosity, and permanent wilting point. The study has shown what factors create a stable soil structure in the forest soils of PNP. 相似文献
30.
To study the tensile mechanical properties of constant resistance bolts, the RFPA (Rock Failure Process Analysis) statics software is used to perform a uniaxial tensile test on a constant resistance bolt. The numerical test results show that the plastic strain value is 12 times the magnitude of the elastic strain. During plastic deformation, the fluctuation in the stress magnitude is relatively stable, indicating that the bolt has good constant resistance characteristics. The numerical test results are in good agreement with the laboratory test results of M.C. He, and the accuracy and reliability of the numerical test method are verified. Therefore, the RFPA software with coupled static-dynamic loading is further adopted to study the supporting effects of traditional bolts and constant resistance bolts under coupled static-dynamic loading. The numerical comparison of the test results show that the constant resistance bolts can effectively control the deformation amount and rate of the laneway surrounding rock, reduce the total and rate of increase in the accumulated acoustic emissions, decrease the stress on the units in the model and protect the stability of the laneway. This paper verifies that a constant resistance bolt has better impact resistance mechanical properties than those of a traditional bolt and provides an effective way to control rock burst and soft rock that is prone to large deformation damage. 相似文献