Numerical investigation of fracture behavior of tunnel by excavation loading

A rock failure process analysis model, RFPA2D code, a two-dimensional numerical code, were proposed. The code not only satisfied the global equilibrium, strain consistent and nonlinear constitutive relationship of rock and soil materials but also took into account the heterogeneous characteristics of rock materials at macroscopic and microscopically level. The failure behavior of tunnel could be simulated by this numerical model. The model could realistically simulate the fracture behavior of tunnel by excavation loading, strength limits, and post peak response for both tension and compression. As the proposed method was used to conduct the stability analysis of tunnel, the safety factor of tunnel was defined as the ratio of actual shear strength parameter to critical failure shear strength parameter. Not only the safety factor of tunnel with specific physics meaning can be obtained, but also the overall failure process and the location of failure surface may also be determined at the same time.     

钙质砂地基中桶形基础垂直动载响应实验研究

首先进行了垂直静极限承载力实验,为确定垂直动载荷幅值的选择提供参考。然后重点针对栽荷幅值和频率的影响进行了系列的室内小模型实验,并对结果进行了分析,获得了垂直动载下桶形基础在钙质砂地基中的响应特点。     

降水防砂复合材料的研究与应用

针对大港油田疏松砂岩区块含水上升快、出砂加剧,常规防砂工艺技术无法解决既防砂又能有效降水的问题,研制出了一种自身可固结的颗粒型降水防砂复合材料（粒径0.3～0.5,0.5～0.7和0.7～1.4 mm）。采用正交试验进行了材料配方优选,并对优选出的材料进行了固化温度和固化时间对人工岩心固结强度和渗流能力的影响评价、耐酸碱介质性能评价和岩心稳定性评价。结果表明:该系列降水防砂复合材料适用于井温30～80 ℃的油井,人工岩心抗压强度大于3 MPa,液相渗透率0.3～0.8 μm2（根据粒径可以调节）。该降水防砂复合材料在大港油田成功实施了16井次,防砂施工成功率100%,防砂有效率93.8%,平均降水率达14.7%,取得了较好的降水防砂效果。      

高黏度牛顿流体中砂粒运动实验研究

为了解决疏松砂岩稠油油藏开采过程中的砂粒运移问题,基于固液两相流理论及实验流体力学理论,利用研制的高黏度流体颗粒自由沉降实验装置,分别开展了高黏度牛顿流体中球形颗粒的自由沉降实验、砂粒的自由沉降实验和不同含砂体积分数下混合黏度变化规律实验,根据实验结果,建立了不同粒径范围的阻力系数模型以及混合黏度模型。研究表明,高黏油混合黏度存在相应的临界值,在实验条件下,含砂体积分数为0.1%时,混合黏度达到最低,不利于携砂。结合上述模型和实验结果,建立了高黏度牛顿流体中的砂粒运动模型,揭示了高黏介质中颗粒的特定运移规律,为今后稠油携砂流动规律理论研究奠定了基础。      

砂土强度和剪胀性的颗粒力学分析

基于广义塑性理论与临界状态概念,研究提出了一个统一三维砂土本构模型,通过一组参数实现了砂土由压缩至剪切过程中状态参量的统一表述。基于ABAQUS提供的用户自定义材料子程序UMAT接口,利用Fortran语言编程实现了该三维弹塑性本构关系模型在软件中的二次开发。分别利用Toyoura砂、Fuji River砂以及Tokachi砂的剪切试验数据与数值模拟结果进行对比,结果表明：提出的有限元计算模型可以有效反映加载过程中不同围压和砂土初始密度对应力-应变曲线的影响,能够准确描述密砂的剪胀特性与应变软化特性以及松砂的剪缩特性与应变硬化特性,从而更加真实地反映三维应力状态下土的变形和强度特性。研究成果进一步扩展了ABAQUS在岩土工程中的应用范围,能够为岩土工程领域的数值分析计算提供更加快捷的解决方案。     

有限元分析在解决沙漠胎66×44.00-25径向裂口的应用

利用有限元分析66×44.00-25径向裂口原因,探究产生机理,提出改进方向。结果表明：通过调整胎体和缓冲帘线角度、提高胶料的耐屈挠和耐老化性能,可以解决66×44.00-25早期径向裂口。     

Analysis of deep excavations in clay under the undrained and plane strain condition with small strain characteristics

The nonlinearity and small strain characteristics of clay are predominant factors to affect the analysis accuracy of surface settlement induced by deep excavation in soft clay. In this study, we use a newly developed constitutive model, namely the undrained soft clay model, to simulate the nonlinearity of soft clay and to describe the degradation of elastic Young's modulus with the increasing stress level, ranging from small strain to near failure. The parameters of the formula can be obtained from conventional soil tests. One well-documented case history is then used to show the parameter determination procedure and validate the proposed model. The states of strain and stress paths for the soil in the excavation are also studied to validate the rationality of the model. Besides, two additional case studies are conducted to verify the model further.     

电感耦合等离子体原子发射光谱-内标法测定优质石英砂中8种杂质组分

优质石英砂主要成分为SiO₂,其中的杂质直接影响其品质。通常杂质的测定方法如分光光度法和原子吸收光谱法,存在流程长、不能多组分同时测定等问题,难以满足实际检测需求。实验采用氢氟酸、硝酸、高氯酸分解样品,加入In标准溶液作内标,简化实验流程,消除基体效应、仪器漂移及定容体积不准确造成的测定误差,建立了电感耦合等离子体原子发射光谱(ICP-AES)-内标法测定优质石英砂中Al₂O₃、Fe₂O₃、TiO₂、CaO、MgO、K₂O、Na₂O、P₂O₅等8种杂质组分的方法。在各组分校准曲线线性范围内,线性相关系数在0.999 4～1.000 0之间;方法中各组分的检出限为0.000 1%～0.003 8%(质量分数)。按照实验方法测定石英岩标准物质GBW07837中的各待测组分,结果的相对标准偏差(RSD,n=12)为0.92%～6.6%,测定值和认定值相吻合。采用实验方法对优质...     

三台阶七步法在软岩隧道应用技术探讨

探讨了三台阶七步法在软岩隧道中的应用,对超前地质预报、加强支护、步距控制、监控量测等关键技术进行了分析,并与双侧壁导坑开挖法、CRD法等进行了比较,总结归纳了该法的优点,以期更加完善的推广应用该工法。     

玻璃钢加砂管在软土地基中的应用

主要分析并指出了新型材料在软土地质环境中的应用,并提出了解决软土中存在问题的方法,保证了新型材料在不同的条件正常施工,从而保证了管网的安全运行。