岩土力学数值模拟中力学参数的确定方法

力学参数的选取是进行岩土力学数值模拟的关键，它直接决定了模拟结果的合理性。不同的力学模型需要选取不同的计算参数，经验值在参数的确定过程中具有一定程度的参考价值，几种变形参数和强度参数的现场尺度转化方法解决了室内土工实验参数的现场应用问题，提出了进行力学参数和计算模型合理确定的推断模型的概念，并对推断模型实现的思想和步骤进行了较为详细的讨论。     

公路隧道通风竖井岩爆机制颗粒流模拟研究

根据工程地质资料分析,岩爆是秦岭公路隧道2号通风竖井施工过程中的主要难题。岩爆机制是指岩爆发生的物理过程,与岩石的颗粒大小、颗粒胶结和粒间孔隙等结构特征密切相关。根据颗粒流基本理论和竖井混合片麻岩的基本力学特性,进行混合片麻岩细观颗粒参数标定研究。颗粒大小不是一个自由参数,通过颗粒流模拟的相似比分析,采用强度折减方法进行竖井岩爆机制的颗粒流模拟。研究表明,岩爆孕育的细观机制为平行于开挖面的微裂纹萌生-微裂纹扩展、聚合-宏观裂纹的形成,为压致张剪断裂破坏,主要是由张拉裂纹扩展、聚合引起的,是一个渐近破坏过程。研究成果为竖井岩爆稳定性分析提供初步依据。     

深埋隧洞爆破开挖扰动损伤效应的数值模拟

爆破开挖扰动是深埋隧洞损伤区孕育及演化的重要影响因素。根据隧洞岩体钻爆开挖过程分析了爆炸荷载及开挖荷载瞬态卸荷对岩体的扰动作用,基于LS-DYNA动力有限元程序,提出了利用施加节点反力模拟待开挖隧洞岩体的约束作用,通过控制节点反力的变化过程以模拟开挖荷载瞬态卸荷,采用爆炸荷载变化曲线模拟爆炸作用过程的爆破开挖扰动数值模拟方法,并利用该方法模拟分析了爆破开挖扰动对围岩的损伤效应,结果表明,应力重分布对围岩损伤最大,隧洞围岩损伤区主要由围岩初始应力重分布所导致,爆炸荷载作用将增大围岩损伤区范围,考虑开挖荷载瞬态卸荷作用的围岩损伤区最大,且地应力越高,开挖荷载瞬态卸荷作用对围岩的损伤效应越显著     

某软土地区深基坑开挖数值模拟分析

以某软土地区深基坑开挖为背景,运用有限元方法计算模拟了基坑开挖的不同阶段,分析不同工况下基坑及周围土体的变形和受力情况,并对不同施工方式下基坑变形和受力进行了对比分析。数值分析表明软土地区深基坑开挖时,需采取相应的施工措施,控制基坑变形和受力,确保工程安全顺利进行。研究结论可为类似工程提供借鉴与参考。     

裂隙参数分析在岩体力学和水力学习性研究中的应用

岩体的力学和水力学习性主要取决于其中裂隙的发育程度。一定成因的裂隙具有一定的发育规律,这一规律既具确定性又具随机性。本文详细讨论了表示岩体裂隙发育程度特征参数的量测和分析方法,重点论述了裂隙参数分析在研究岩体渗透习性、岩体中裂隙网络计算机模拟及岩体弹性参数分析等方面的应用。     

Genesis of lithium pegmatites from the leinster granite margin,southeast ireland: Geochemical constraints

Extensive and economically-important lithium pegmatites have been described from the eastern flank of the large S-type peraluminous Leinster Granite batholith in southeast Ireland. This flank area is also the locus of a major dip-slip ductile shear zone which was active during emplacement of the Tullow Lowlands pluton of the batholith. All the known bedrock occurrences of lithium pegmatite are contained within this marginal deformation zone. Most previous studies have suggested derivation of the lithium pegmatites by fractionation from the Leinster Granite itself, though none are conclusive. More recently, an anatectic model has been proposed whereby the pegmatites were derived by melting of Li-rich sediments adjacent to the batholithic contact. Our investigation has been concerned with a detailed study of the Rb-Sr isotope systematics and trace element geochemistry of the pegmatites and their host granitoids in an attempt to resolve the problem of pegmatite genesis. The results suggest a strong geochemical and temporal coherence between the Leinster Granite and the lithium pegmatites. A model is proposed in which Li enrichment in residual magmas may be linked to the development of muscovite instead of biotite in the Leinster Granite itself. The Li excluded from entry to biotite then accumulates in highly mobile, low-viscosity pegmatitic fluids which migrate into the marginal shear zone of the Tullow Lowlands pluton where they crystallize at considerably lower temperatures.     

Shallow landslides in deeply weathered slates of the Sierra de Collcerola (Catalonian Coastal Range, Spain)

Stability conditions in an area located NW of Barcelona (Spain) are discussed. Here, several mass movements were observed, mainly affecting weathered Paleozoic slates. Many of these failures involved slopes cut along recent infrastructures: debris flows, wedge and plane failures, generally surficial, occurred more frequently. After a detailed geological and geomorphologic survey, geomechanic characterization was carried out, according to RMR and SMR classifications. This rating gave a prediction of slope behaviour, in fairly good agreement with the real observed one.

Stability numerical analysis was carried out for the main cut slopes, based upon the Limit Equilibrium Method. First of all, the deterministic factor of safety was computed using the mean values of parameters. After that, a simulation technique based upon the Monte Carlo Method was applied in order to obtain factor of safety distributions. The probability of failure was estimated as P(F<1).

Finally, results from deterministic and probabilistic approaches were compared. The effectiveness of different possible remedial measures was highlighted by means of a sensitivity analysis, which showed that the more important parameters in the study area are the geometrical ones (height, slope and failure plane angles). The final technical solutions adopted are briefly outlined.     

Interpretation of cosmogenic nuclides in meteorites on the basis of accelerator experiments and physical model calculations

Cosmogenic nuclides in extraterrestrial matter provide a wealth of information on the exposure and collision histories of small objects in space and on the history of the solar and galactic cosmic radiation. The interpretation of the observed abundances of cosmogenic nuclides requires detailed and accurate knowledge of their production rates. Accelerator experiments provide a quantitative basis and the ground truth for modeling cosmogenic nuclide production by measurements of the relevant cross sections and by realistic simulations of the interaction of galactic protons with meteoroids under completely controlled conditions, respectively. We review the establishment of physical model calculations of cosmogenic nuclide production in extraterrestrial matter on the basis of such accelerator experiments and exemplify this approach by presenting new experimental and theoretical results for the cosmogenic nuclide⁴⁴Ti. The model calculations describe all aspects of cosmogenic nuclide production and allow the determination of long-term solar and galactic cosmic ray spectra and a consistent interpretation of cosmogenic nuclides in extraterrestrial matter.     

天津市地面沉降数值模拟研究

地面沉降是天津市的主要环境地质问题。造成天津市地面沉降的原因很多,但主要原因是大量开采地下水。本文重点研究开采地下水条件下的地面沉降数学模型及模拟,为控制地面沉降提供科学依据。通过对第四系的水文地质条件分析,建立第四系的水文地质概念模型和地层压缩概念模型,并建立相应的准三维水流数学模型和一维地层压缩数学模型,两者通过含水层水头和弱透水层粘性土中孔隙水头的内在联系耦合在一起。利用以往系列水位数据和沉降数据对模型进行标定,模型基本上反映了天津市地面沉降的实际情况。