重庆走马岭岩溶隧道涌水量初步研究

隧道涌水问题普遍存在,从隧道的施工到竣工运行都受其影响,特别是在南方岩溶地区尤为严重。根据勘察资料,走马岭隧道穿越可溶岩段(含断层破碎带)长1525m,占隧道总长的62%,极易发生隧道涌水事故。本文结合已开挖段隧道涌水的实时监测数据及前期工程勘察资料,对隧道涌水做出初步预测评价,为以后的施工提供依据。     

基于集对分析模型的岩溶区浅埋穿河隧道突涌水危险性评价

在岩溶区修建隧道常会面临突涌水等地质灾害,尤其是对于浅埋穿河隧道的建设,更是极具挑战性的一项工作。由于隧址区存在断层破碎带、岩体风化程度高、节理裂隙发育等,使得河水入侵隧道的可能性大幅增加。为了有效评价岩溶区浅埋隧道下穿河段突涌水发生的危险性,本研究根据隧址区地质条件及隧道特征,选取了地层岩性、修正的岩层倾角、可溶岩与非可溶岩接触带、围岩等级、断层带宽度、断层性质、裂隙发育程度、地表水流量、地表汇水面积、隧道埋深、施工干扰程度共11个影响突涌水的关键因素作为评价指标,建立了岩溶区浅埋穿河隧道突涌水危险性评价体系。首先,采用层次分析法构造判断矩阵确定评价指标的权重,利用集对分析法计算各评价指标的联系度,进而确定评价样本的综合联系度;其次,运用最大隶属度原则识别突涌水风险等级;最后,根据危险性等级与涌水量之间的对应关系,可初步预测突涌水量范围。针对跃龙门隧道下穿高川河浅埋段的突涌水风险,采用集对分析模型进行分析,计算结果显示,危险性评价预测的突涌水量范围为3 000～10 000 m³/d,现场开挖实际涌水量为7 000 m³/d。即危险性评价结...     

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针对红透山深部断层下巷道围岩破坏诱发的涌水现象,以该矿水文地质条件 为基础,建立了岩体水力学模型,应用岩石破裂过程渗流-应力耦合分析系统 (RFPA$^{\rm 2D}$-Flow)模拟研究了深部断层下巷道围岩破坏过程：裂隙形成、扩展到突水通 道最终贯通形成涌水的全过程. 通过对损伤区分布、应力场和渗流场的演化规律进行分析, 揭示了巷道应力重新分布诱发损伤及渗流涌水规律,对涌水通道进行模拟定位,为红透山铜 矿深部巷道支护防渗设计提供了科学依据.     

采动对承压底板断层活化及突水危险性的影响分析

随着煤炭开采深度的增加，受奥灰岩溶底板高承压水的威胁日趋严重，矿井突水事故的频率不断增加，尤其是含断层构造的奥灰岩溶承压底板的情形。本文建立弹塑性多孔介质渗流应力耦合模型；并基于此耦合模型，应用多物理场数值模拟软件COMSOL Multiphysics和MATLAB软件编程，结合徐州某矿突水实例，分析了采动影响下承压采...     

铁路深埋隧道区岩溶发育特征研究

对圆梁山隧道毛坝向斜段揭露溶洞进行分析的基础上 ,结合向斜区岩溶分布的勘察 ,对毛坝段深层岩溶发育特征及影响因素进行了研究。认为岩溶水在水力坡度或压力水头 ,尤其是水重力的作用下有不断向深层运移的趋势 ,所以在水具有侵蚀性的前提下 ,岩溶也具有向深层发育的趋势 ,并在厚层隔水底板及排泄基准面附近形成岩溶较发育带。而岩溶分布的层位及构造部位 ,在同一地质单元中的浅层和深层区具有类似性     

岩溶塌陷的类型、成因机制及防治途径──兼论武汉市岩溶塌陷勘查工作要点

按岩溶塌陷的类型, 对其成因机制作了分析。在此基础上, 提出了武汉市岩溶塌陷勘查与防治工作要点。     

宜万铁路八字岭隧道岩溶管道冲积物特征实验研究

岩溶山区的隧道工程建设中,隧址区的岩溶管道连通性对隧道设计中涌水量、水压力等指标的确定以及隧道施工防灾具有重要意义。以宜万铁路八字岭隧道为例,系统分析了岩溶管道粗颗粒沉积物的粒度、岩石及矿物成分、圆度度组合等特征,通过对比分析,探讨了碎屑沉积物的地质联系,研究了沉积物的来源,以此为基础分析了隧址区岩溶管道的连通性,为工程设计施工提供参考。     

平果铝平南赤泥堆场岩溶地质问题与防治技术

平果铝平南赤泥堆场地内受过构造强烈挤压作用的白云质灰岩可溶性中等但裂隙极为发育,在年降水量大（年均1374.2mm）、年蒸发量大（年均1572.6mm）、气温高（年均21.8°C）的气候条件下,岩溶沿地质构造呈带状不均匀发育,形成了14个不同发育程度的岩溶区。堆场内浅表岩溶较深部岩溶发育,浅表岩溶的主要形态有落水洞、溶沟（槽）,深部岩溶的主要形态是溶蚀裂隙。堆场内岩溶形成了小型树枝状的暗河网,且与场外地下水相联通。堆场内岩溶的渗漏有管道集中渗漏和裂隙分散渗漏两种类型,按渗漏强度可分为强岩溶渗漏区、中等岩溶渗漏区和弱岩溶渗漏区。强岩溶渗漏区的防渗措施是对于中小型的岩溶先充填,大的岩溶用盖板跨越,然后再进行防渗铺盖,其他两区则先充填、整平,再进行防渗铺盖。     

铁路施工期岩溶地质宏观预测专家系统研究

岩溶的发育受到多种因素控制,具有不确定性,在结合宜万铁路齐岳山隧道、八字岭隧道、野三关隧道、马鹿青隧道以及渝怀铁路圆梁山隧道等多座岩溶地区山岭隧道的岩溶洞穴发育分布特征分析研究的基础上,提出了包括地层岩性、地质构造、地形地貌、地表水、地下水、隧道设计等因素在内的隧道工程岩溶超前预报的地质分析指标体系,明确了岩溶灾害发生危险性的高、中、低3个等级的工程地质标志性特征,应用专家评价法研究了各个指标的权重,构建了超前地质预报专家系统知识库,研制了山岭隧道岩溶超前地质预报专家系统,通过宜万铁路具体隧道工程的实际应用探讨了专家系统预测的可靠性。     

岩溶地面塌陷危险性模糊评价方法

岩溶地面塌陷危险性评价是一个复杂而亟待解决的问题,本文针对岩溶地面塌陷危险性评价的特点,在综合考虑影响岩溶地面稳定性的多种因素的基础上,引入系统层分析方法和多级模糊评价方法,并以正态函数为隶属函数,以实数的加乘运算作为合成运算规则,建立了岩溶地面塌陷危险性评价的二级模糊评价模型,并将评价结果分为:稳定、较稳定、较不稳定和不稳定4级。应用于广州市某建设场地地质灾害评估工程,结果表明该方法具有良好的可靠性。     

Chaos in a non-autonomous nonlinear system describing asymmetric water wheels

We derive a water wheel model from first principles under the assumption of an asymmetric water wheel for which the water inflow rate is in general unsteady (modeled by an arbitrary function of time). Our model allows one to recover the asymmetric water wheel with steady flow rate, as well as the symmetric water wheel, as special cases. Under physically reasonable assumptions, we then reduce the underlying model into a non-autonomous nonlinear system. In order to determine parameter regimes giving chaotic dynamics in this non-autonomous nonlinear system, we consider an application of competitive modes analysis. In order to apply this method to a non-autonomous system, we are required to generalize the competitive modes analysis so that it is applicable to non-autonomous systems. The non-autonomous nonlinear water wheel model is shown to satisfy competitive modes conditions for chaos in certain parameter regimes, and we employ the obtained parameter regimes to construct the chaotic attractors. As anticipated, the asymmetric unsteady water wheel exhibits more disorder than does the asymmetric steady water wheel, which in turn is less regular than the symmetric steady state water wheel. Our results suggest that chaos should be fairly ubiquitous in the asymmetric water wheel model with unsteady inflow of water.     

三河口碾压混凝土拱坝温控仿真研究

针对三河口碾压混凝土拱坝温度控制问题,综合考虑外界气温和混凝土热、力学性质随时间变化的影响,采用施工全过程仿真分析方法,动态模拟大坝碾压混凝土入仓温度、分层铺筑方式、通水冷却、后期养护等施工参数;分析了坝体温度场和温度应力场,提出了大坝温度、应力控制标准;根据计算结果及时进行温控方案的动态比较和调整,制定了具体的温控防裂要求和措施;在施工中对比实测监测数据。结果表明:坝体温度、应变的数值基本符合坝体温度控制的设计要求,证明温控措施有效。     

某大型水电枢纽坝基埋藏型岩溶发育特征及深层承压水研究

作者在现场工程地质勘察、试验基础上, 对我国西南某大型水电枢纽坝基所遇特殊的复杂埋藏型岩溶、承压水问题进行了研究, 弄清了坝基岩溶、承压水形成条件及发育特性, 对坝址选择及工程处理的决策具有重要意义。     

三峡水库应力场对水田坝断裂影响的数学-力学模型研究

水库蓄水后, 在一定空间范围内形成了应力场、应变场和渗流场。我们建立了一个数学一力学模型, 以描述水压应力场的特征。通过运用弹塑性岩土体非线性应力一应变和稳定性静力分析NOLM83二维有限元程序发现, 水库水压应力场的最大主应力从水库中心向两侧、从水库表面向深部逐渐降低。在此基础上, 研究了在未来三峡水库水压应力场影响下, 水田坝断裂的应力、应变和影响范围。研究表明, 平面影响范围为该断裂两侧5～-6km.由于岩体的浮托作用, 地表面的累积位移量少于10mm, 并向下逐渐减小。因此, 水田坝断裂完全能够承受三峡水库蓄水后产生的水压应力, 不会出现中-强度水库诱发地震, 不会影响三峡工程的安全。     

碾压混凝土浇筑层温度场计算模型研究

碾压混凝土浇筑层的初始温度和绝热温升是碾压混凝土坝设计中的常见问题之一,直接关系到温度场仿真计算的精度和计算量问题。本文考虑各碾压层混凝土浇筑时间和水化热散发时间的不同,应用Laplace变换法和叠加原理求出了多层板状结构体的一维温度场理论解答。然后以此解析解为基础,合并多个碾压层为一个浇筑层,建立了温度场等效模型,并给出了复合浇筑层的等效初始温度和等效绝热温升的计算方法。本文的方法能够较好地模拟碾压混凝土分层碾压的施工过程,便于温度场有限元计算,计算结果表明,该方法具有较高的精度。     

基于雷诺应力模型的平衡大气边界层模拟

基于雷诺应力湍流模型（简称RSM模型）,研究了平衡大气边界层风场数值模拟问题．假设流体不可压,且不计雷诺应力输运方程中的对流项、浮力产生项、系统旋转产生项和扩散项,在准各向同性的条件下,推导出RSM模型湍动能k的表达式是标准k-ε模型k常数表达式的0.893倍．考虑k沿高度变化的修正,根据在标准k-ε模型中满足水平均匀性的湍流来流边界条件,提出在RSM模型中产生平衡大气边界层的湍流来流边界条件．基于空风洞的数值模拟结果表明,与工程上常用的湍流来流边界条件相比,基于本文提出的湍流来流边界条件得到的风场水平均匀性更优,且在整个流域内,得到的雷诺应力剖面更合适．从而验证了该湍流来流边界条件的适用性．     

Dynamics of algae blooming: effects of budget allocation and time delay

Algal blooms are increasing in coastal waters worldwide. The study on the features of algal pollution in water bodies and the ways to eliminate them is of vital importance. Preventing, treating, and monitoring algal blooms can be an unanticipated cost for a water system. To tame algal bloom in a lake, the government provides funds through budget allocation. In this paper, we propose a mathematical model to investigate the effect of budget allocation on the control of algal bloom in a lake. We assume that the growth of budget follows logistic law and also increases in proportion to the algal density in the lake. A part of the budget is utilized for the control of inflow of nutrients, while the remaining is used in the removal of algae from the lake. Our results show that algal bloom can be mitigated from the lake by reducing the inflow rate of nutrients to a very low value, which can be achieved for very high efficacy of budget allocation for the control of nutrients inflow from outside sources. Also, increasing the efficacy of budget allocation for the removal of algae helps to control the algal bloom. Further, more budget should be used on the control of nutrient’s inflow than on the removal of algae, as the presence of nutrients in high concentration will immediately proliferate the growth of algae. Moreover, the combined effects of controlling the inflow of nutrients and removing algae at high rates will result in nutrients and algae-free aquatic environment. Further, we modify the model by considering a discrete time delay involved in the increment of budget due to increased density of algae in the lake. We observe that chaotic oscillations may arise via equilibrium destabilization on increasing the values of time delay. We apply basic tools of nonlinear dynamics such as Poincaré section and maximum Lyapunov exponent to confirm the chaotic behavior of the system.

     

Development of inflow turbulence in microscale urban atmospheric environment

The sensitivity of turbulence-development to inflow turbulent statistics is investigated in microscale urban atmospheric environment flows. Large-eddy simulations(LESs) are carried out, in which the inflow error is brought in by transforming a fully developed turbulent field according to the Reynolds stress or energy spectra. A theoretical analysis is performed by neglecting the diffusion term in the budget equations of the turbulent kinetic energy. The results show that,(i) the error caused by the Reynolds stress decays until the fully developed level is achieved, and(ii) the error caused by the characteristic length scale increases immediately and then decreases. The streamwise changing rate of the inflow error weakens when the vertical coordinate increases. Further testing of the effects of the inflow inner-and outer-layer data shows that, the inflow innerlayer data dominate the near field, and the inflow outer-layer data dominate the far field.     

A N‐dynamics Model for Predicting N‐behavior Subject to Environmentally Friendly Fertilization Practices: II –Numerical Model and Model Validation

Nitrogen dynamics in the soil under the condition of environmentally friendly fertilization practices (EFFPs) is described by a comprehensive Ndynamics model. The model (first paper of this series, Transport in Porous Media 31(3) (1998), 249–274) is different from other models in its capability of simulating the special phenomena related to the application of EFFPs. In this paper, a finite difference method is used to solve the mathematical model. The numerical model is verified by simulating several water flow and conservative solute transport problems with existing numerical or analytic solutions. The good agreements between our simulation results and the solutions given by others show that our model is reliable in simulating flow and transport problems in the soil. Preliminary model validation is conducted by applying the model to simulate two field experiments. The acceptable agreements between our numerical simulation results and experimental data demonstrate that the model can reasonably model Ndynamics in the soil under field conditions.