分布埋入式光纤与隧道衬砌耦合性能试验及应用

为探究埋入式光纤与隧道衬砌的耦合性能,分别从理论与试验两个方面进行研究,并在实际工程中进行了验证。构建了光纤、中间体和基体结构力学分析模型,进行光纤应变传递机制理论分析,计算了光纤应变传递效率;使用钢筋混凝土梁模拟隧道衬砌,进行了2组不同加载速率的试验。其中,在同一根梁内(同一工况)设计6种光纤的布设方式,以位移控制的方式在梁跨中部位进行单点多级加载,使用BOFDA(布里渊散射光频域分析)技术分别对6条光纤进行监测。试验结果表明:6条光纤均可以有效监测梁从开始加载至钢筋开始屈服阶段,光纤与梁耦合性最好;钢筋开始屈服直至梁破坏阶段,光纤应变不再增加甚至减小或呈现出光纤断裂的状态,此过程光纤与梁耦合性较差;除开槽埋入式光纤的有效监测应变差为3 000×10^-6外,其余布设方式光纤有效监测应变差为2 000×10^-6;光纤在长距离(>>146 mm)埋入式布设情况下可认为其应变传递效率接近100%,2组不同试验结果呈现相似规律。在北京市新机场线地铁暗挖隧道CRD工法区间进行了工程应用研究,监测结果表明分布埋入式光纤布设工艺是可行的,可为...     

钱家店铀矿床表生含氧含铀流体与深层酸性含烃流体的耦合成矿作用——来自岩心蚀变矿物填图的证据

以岩心光谱蚀变矿物填图为主要研究手段,结合野外地质编录、偏光显微镜、扫描电镜、电子探针能谱分析、氢氧同位素测试等方法,对开鲁盆地钱家店砂岩型铀矿床85个有效钻孔岩心开展了系统的蚀变矿物填图和矿物学研究。结果表明:①主要含矿层上白垩统姚家组蚀变矿物主要有黏土矿物(高岭石、蒙脱石、伊利石、伊/蒙混层及局部绿泥石)、铁的三价氧化物、黄铁矿、碳酸盐(方解石、白云石、铁白云石)等,它们呈现明显的分带特征:氧化带为高含量的"高岭石+Fe³⁺氧化物"组合、过渡带为中等含量的"高岭石+蒙脱石(伊/蒙混层)"+高含量的"黄铁矿+铁白云石"组合;还原带则主要为高含量的"蒙脱石(伊/蒙混层)+伊利石+黄铁矿"组合,矿体主要分布在氧化-还原过渡带和高岭石变化的梯度带上,并见有明显的高岭石、黄铁矿、铁白云石富集。②含氧含铀流体主要来自于WS、WN方向,其次为ES方向(也可能是WS向流体的分支),酸性含烃流体主要来自于NE向的断裂构造,流体温度介于40～120℃,两种不同性质流体的耦合作用是该地区的主成矿作用。③主成矿事件应发生在白兴吐"天窗"构造隆升之后,构造天窗在成矿系统中主要承担着还原...     

多尺度孔隙岩石的核磁共振扩散耦合现象及其探测方法

油藏岩石的孔隙连通性是反映流体渗流难易程度的重要参数,对渗透率、有效孔隙度等岩石物理参数的评价具有重要作用.连通的孔隙中,核磁共振（NMR）弛豫的交换会产生扩散耦合现象,可作为孔隙连通性的表征和探测方法.本文提出利用横向弛豫T₂-T₂脉冲序列测量岩石的扩散耦合现象.运用随机游走方法模拟多孔岩石的核磁共振响应特征,分析扩散耦合的影响因素,推导表征扩散耦合强度的弛豫交换速率计算公式.结果表明：孔隙间的扩散耦合强度与T₂-T₂脉冲序列的混合时间呈正相关性,基于双孔弛豫交换模型推导的弛豫交换速率计算公式能够准确表征双尺度孔隙系统的扩散耦合强度.在孔隙尺寸不满足快扩散条件时,会出现与扩散耦合无关的非对角峰信号.针对含多类型孔隙的碳酸盐岩模型,随混合时间的增加,扩散耦合强度变大,一维T₂谱的形态畸变程度加重,在T₂-T₂二维谱中,代表微裂缝、粒间小孔、溶蚀大孔的信号能量变化趋势不同,反映不同类型孔隙间的连通性存在差异.本文的分析与讨论丰富了核磁共振弛豫在岩石物理性质评价中的应用方向,对利用核磁共振评价复杂孔隙岩石的孔隙结构和连通性提供了新思路和新方法.

     

考虑几何非线性的强夯流固动力耦合分析

针对强夯法加固地基机理的流固动力耦合分析问题,本文考虑土体的几何非线性,建立土体非线性动力平衡方程和整体流固动力耦合方程,给出土体非线性动力平衡方程的迭代计算格式和流固动力耦合方程的解耦计算方法,并对一具体算例进行了数值分析,得到了地基位移、应力等在强夯作用下的变化规律和在空间上的分布特征,为精确模拟分析强夯加固机理提供了有效途径.     

橡胶砂弹性动力学参数的弯曲-伸缩元试验研究

橡胶砂作为一种廉价环保的土工材料,应用前景十分广阔,关于其力学特性的研究具有重要意义。采用弯曲–伸缩元法对橡胶砂进行了剪切波和压缩波联合测试,分别采用离散频率扫描法和初达波法确定了剪切波和压缩波的传播时间,进而得到其弹性动力学参数:初始剪切模量、侧限模量和泊松比,分析了橡胶含量和围压对橡胶砂弹性动力学参数的影响。结果表明:在同样围压下,随着橡胶含量的增加,橡胶砂初始剪切模量和侧限模量逐渐减小,初始泊松比逐渐增大;在同样橡胶含量下,随着围压的增大,橡胶砂初始剪切模量和侧限模量逐渐增大,初始泊松比逐渐减小。最后,在此基础上进行了两种因素耦合效应的分析以及相关力学机制的探讨。     

Implicit integration under mixed controls of a breakage model for unsaturated crushable soils

This paper discusses a series of stress point algorithms for a breakage model for unsaturated granular soils. Such model is characterized by highly nonlinear coupling terms introduced by breakage‐dependent hydro‐mechanical energy potentials. To integrate accurately and efficiently its constitutive equations, specific algorithms have been formulated using a backward Euler scheme. In particular, because implementation and verification of unsaturated soil models often require the use of mixed controls, the incorporation of various hydro‐mechanical conditions has been tackled. First, it is shown that the degree of saturation can be replaced with suction in the constitutive equations through a partial Legendre transformation of the energy potentials, thus changing the thermomechanical state variables and enabling a straightforward implementation of a different control mode. Then, to accommodate more complex control scenarios without redefining the energy potentials, a hybrid strategy has been used, combining the return mapping scheme with linearized constraints. It is shown that this linearization strategy guarantees similar levels of accuracy compared with a conventional strain–suction‐controlled implicit integration. In addition, it is shown that the use of linearized constraints offers the possibility to use the same framework to integrate a variety of control conditions (e.g., net stress and/or water‐content control). The convergence profiles indicate that both schemes preserve the advantages of implicit integration, that is, asymptotic quadratic convergence and unconditional stability. Finally, the performance of the two implicit schemes has been compared with that of an explicit algorithm with automatic sub‐stepping and error control, showing that for the selected breakage model, implicit integration leads to a significant reduction of the computational cost. Such features support the use of the proposed hybrid scheme also in other modeling contexts, especially when strongly nonlinear models have to be implemented and/or validated by using non‐standard hydro‐mechanical control conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

The influence of coupled physical swelling and chemical reactions on deformable geomaterials

Coupled thermo‐hydro‐mechanical‐chemical modelling has attracted attention in past decades due to many contemporary geotechnical engineering applications (e.g., waste disposal, carbon capture and storage). However, molecular‐scale interactions within geomaterials (e.g., swelling and dissolution/precipitation) have a significant influence on the mechanical behaviour, yet are rarely incorporated into existing Thermal‐Hydro‐Mechanical‐Chemical (THMC) frameworks. This paper presents a new coupled hydro‐mechanical‐chemical constitutive model to bridge molecular‐scale interactions with macro‐physical deformation by combining the swelling and dissolution/precipitation through an extension of the new mixture‐coupling theory. Entropy analysis of the geomaterial system provides dissipation energy, and Helmholtz free energy gives the relationship between solids and fluids. Numerical simulation is used to compare with the selected recognized models, which demonstrates that the swelling and dissolution/precipitation processes may have a significant influence on the mechanical deformation of the geomaterials.     

A two‐dimensional coupled hydromechanical discontinuum model for simulating rock hydraulic fracturing

Within the framework of our discontinuous deformation analysis for rock failure algorithm, this paper presents a two‐dimensional coupled hydromechanical discontinuum model for simulating the rock hydraulic fracturing process. In the proposed approach, based on the generated joint network, the calculation of fluid mechanics is performed first to obtain the seepage pressure near the tips of existing cracks, and then the fluid pressure is treated as linearly distributed loads on corresponding block boundaries. The contribution of the hydraulic pressure to the initiation/propagation of the cracks is considered by adding the components of these blocks into the force matrix of the global equilibrium equation. Finally, failure criteria are applied at the crack tips to determine the occurrence of cracking events. Several verification examples are simulated, and the results show that this newly proposed numerical model can simulate the hydraulic fracturing process correctly and effectively. Although the numerical and experimental verifications focus on one unique preexisting crack, because of the capability of discontinuous deformation analysis in simulating block‐like structures, the proposed approach is capable of modeling rock hydraulic fracturing processes. Copyright © 2014 John Wiley & Sons, Ltd.     

PPP/SINS紧耦合系统仿真的研究与分析

在捷联惯导(SINS)和GPS卫星接收机进行紧耦合的研究中,采用差分定位进行紧耦合的方法比较成熟,而关于精密单点定位(PPP)与捷联惯导紧耦合的研究还比较少。本文对精密单点定位与捷联惯导紧组合系统进行了Matlab仿真,利用数学解析的方法产生机载运动轨迹,通过设置系统的参数,获得仿真SINS和GPS数据;然后,通过PPP/SINS紧组合系统的仿真程序解算,将定位结果与PPP的结果比较,表明PPP/SINS紧组合导航定位的结果比PPP的精度和可靠性好,而且收敛的速度更快,同时也验证了算法的正确性。最后,分析了不同等级惯导对定位精度的影响。