60KN级涨壳式中空注浆锚杆预应力模拟试验

本文介绍60KN级涨壳式中空注浆锚杆预应力模拟试验目的、过程、方法、结果并提出建议。

环境应力筛选与应力激发试验

结合工程实践体会,探讨了GJB1032对环境应力筛选规定的几点不合适的要求。通过回顾环境应力筛选的发展,指出了环境应力筛选本质上是一种应力激发试验。并简要介绍了应力激发试验。

渤中坳陷中部地区构造应力场光弹模拟实验研究

在对渤中地区沉积构造详细分析的基础上,明确了其中部地区断裂的分布特征,采用以E44-6101型环氧树脂为基体,顺丁烯二酸酐为固化剂,邻苯二甲酸二丁脂为增塑所配制的材料制成渤中中部地质结构模型,对渤中坳陷中部地区构造应力场进行了光弹实验模拟,再现了近北北东向和近东西向断裂在晚近构造格局下的应力状态及分布。试验证明,在构造应力场的作用下,油气往往由高应力值区向低应力值区迁移,而且渤中地区自新近系以来,最大主压应力方向比较稳定。基于试验结果的分析,对北北东向和近东西向两组断裂在晚近应力场的作用下的构造特征及其对油气的控制作用进行讨论。由于渤中坳陷是中国的油气主要产地,通过研究盆地构造应力场的分布,可为盆地的油气勘探和开发提供依据。

环境应力筛选应用研究

结合工程实践,用严谨的理论论述了GJB1032对环境应力筛选规定的几点不合适的要求。通过回顾环境应力筛选的发展历史,指出了环境应力筛选本质上是一种应力激发试验。

Mechanical properties and reinforcement effect of jointed rock mass with pre-stressed bolt

Pre-stressed bolt anchorage is the key technology for jointed rock masses in rock tunnelling,slope treatment and mining engineering.To investigate the mechanical properties and reinforcement effect of jointed rock masses with pre-stressed bolts,in this study,uniaxial compression tests were conducted on specimens with different anchoring types and flaw inclination angles.ABAQUS software was used to verify and supplement the laboratory tests.The laws of the uniaxial compressive strength(UCS)obtained from the numerical simulations and laboratory tests were consistent.The results showed that under the same flaw angle,both the UCS and elastic modulus of the bolted specimens were improved compared with those of the specimens without bolts and the improvements increased with an increase in the bolt pre-stress.Under the same anchoring type,the UCS and elastic modulus of the jointed specimens increased with an increase in the flaw angle.The pre-stressed bolt could not only restrain the slip of the specimens along the flaw surface but also change the propagation mode of the secondary cracks and limit the initiation of cracks.In addition,the plot contours of the maximum principal strain and the Tresca stress of the numerical models were influenced by the anchoring type,flaw angle,anchoring angle and bolt position.

Stretch rate and deformation for pre-stretching aluminum alloy sheet

Numerical simulation combined with experimental test was carried out to analyze the pre-stretching process of the 7075 aluminum alloy sheet,from which the stress variation curves and residual stress of aluminum alloy sheet in different stretch rates were obtained.The results show that the residual stress in length direction is released after unloading the stretch force,while the residual stress in width direction is released during the stretching process.The study of residual stress elimination is beneficial for optimizing stretch rate on the basis of residual stress distribution law.By comparing the variation principle of residual stress in length direction,the size range of three deformation areas and elimination percentage of residual stress were obtained.The residual stresses of clamping area and transition area are not eliminated effectively,so sawing quantity should be the sum of both the areas.The elimination rate of residual stress in even deformation area could reach 90% after choosing a proper stretch rate,which is verified by both simulation and experiment.

Stress-strain analysis of loess triaxial shear test by PFC^(3D)

In order to compensate for limitations of microscopic study on loess triaxial tests, taking the loess in Longxi area as an example, the authors established the loess triaxial test model by using PFC3D software and simulating tfiaxial shear test under the different confining pressures in 0 kPa, 50 kPa and 300 kPa. Compared with laboratory triaxial shear test, the numerical simulation test has a guiding role in loess mechanical strength analysis.

Numerical simulation of crack propagation by manifold method

In this paper, by means of the maximum circle tensile stress on curve of constant ω and stress intensity factors by a path independent contour integral method, trajectories of maxed mode crack propagation are simulated through numerical manifold method. The crack propagation is traced dynamically by modifying the neighboring connection between the crack-top and nodes within elements in the calculating process. This method has the advantages such as less modified area, easiness of programming, high realizability and so on. Then a single sharp nicked specimen is used to verified the numerical result. It is shown that the provided method is reasonable and effective.

NUMERICAL MODELING STUDY OF EFFECTS OF EASTERN PACIFIC WARM POOL ON ENSO

In this study, sensitivity experiments were conducted with the Zebiak-Cane ocean-atmosphere coupled model forced by the wind stress anomaly from the U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data to study the impacts of eastern Pacific warm pool on the formation and development of ENSO events. The effects of climatological mean sea surface temperature of the warm pool on forecast skill during the ENSO events of 1982-1999 are more considerable that those of climatological mean meridional winds and ocean currents. The forecast skill for the 1997/1998 E1 Nifio event is characterized by sensitivity to climatological mean sea surface temperature and anomalies of northerly winds and currents. The forecast skill is found insensitive to climatological mean northerly meridional winds and currents.

基于离散元方法的沥青路面温度应力计算方法及裂缝发育规律

为合理表征沥青混合料的细观特性,并深入研究沥青混合料低温开裂过程中温度应力积累和裂缝扩展的细观机理,基于离散元程序PFC2D建立沥青混合料约束试件温度应力(TSRST)模拟试验方法。根据逆向体视学原理和概率论方法,引入沥青混合料三维体积级配与二维数量级配的转化关系,建立二维离散元虚拟试件;结合沥青混合料各组分之间的接触行为特点,赋予不同的接触本构模型,借助室内试验测定集料和沥青砂浆的宏观参数,推导得到不同温度下各相材料间的细观接触参数;通过TSRST模拟试验,分析试件内部温度场变化规律、温度应力曲线、细观接触力的分布特征以及低温开裂的细观机理。研究结果表明:TSRST离散元模拟和室内试验的结果具有较高的吻合度,断裂温度相对误差为3.7%,断裂强度相对误差为4.8%,TSRST模拟试验具有较高的准确性,能够作为试件低温抗裂性评价的可靠方法;试件的破坏可以分为3个阶段:(1)起裂阶段,在转化点温度前,试件内部个别接触点接触失效,对结构整体受力状况影响较小;(2)稳定扩展阶段,温度达到断裂温度前,随着温度的降低,接触力增加,裂缝沿试件薄弱部位发展,微裂缝数量缓慢稳定增长;(3)不稳定扩展阶段,温度达到断裂温度后,短时间内温度应力下降了66%,裂缝总量增加了132条,微裂缝已汇聚成可见的宏观裂缝,并沿着构造相对薄弱的位置快速扩展,导致试件失去整体承载力。