轴压比对中等高度LC结构剪力墙抗震性能的影响

轻骨料混凝土(L ight-we ight concrete,简称LC)剪力墙的轴压比是剪力墙抗震设计时一个重要的控制因素,直接关系到其延性性能。为使设计规程具有足够的理论依据,本文通过对六榀轻骨料混凝土剪力墙试件的试验,研究了在低周反复荷载作用下,着重考虑不同轴压比对中等高度有边框剪力墙的破坏形态和变形性能的影响效应,对其滞回特性进行分析,计算了各剪力墙的刚度退化率与延性系数,并将无竖缝剪力墙与带竖缝剪力墙的抗震性能进行了对比。     

重锤激发技术在表层调查中的应用

通过对重锤激发的原理、激发能量、采集的同步性等问题的研究以及野外试验,对重锤激发小折射资料的稳定性和可靠性进行了分析,结果表明,激发能量与重锤质量及提升高度成正比,但重锤质量的提高会限制提升高度;足够的重锤质量可保证初至起跳干脆,质量大的重锤初至均好于质量较轻重锤,且大质量重锤可适应的最大偏移距也较大;仪器的稳定性取决于仪器延迟与震板耦合,采用预振可有效提高震板与地表的耦合效果;重锤震源相对炸药来说能量稍弱,但对初至拾取影响较小,解释上百米厚度的表层其误差也仅有几米.重锤作为表层调查中高效的激发设备,已在吐哈探区得到验证.在表层厚度不大于100m的地区,使用重锤震源不仅可降低成本,而且可以彻底摆脱对炸药的依赖,降低安全和环境污染风险.     

Multi-level analysis of field synergy in the displacement mechanisms of heavy oil thermal recovery

One of the major problems of heavy oil thermal recovery is the inadequacy of understanding the multi-field coupling displacement mechanisms to improve the oil production and extraction ratio. From the perspective of “force” and “flow” in thermodynamics, oil displacement fields are divided into three groups: destination, driving and resistance potential fields. Based on the seepage law, the compositional structure of driving and resistance potential fields has been established by making use of non-equilibrium thermodynamics. In addition, coupling indexes among driving, resistance and a combination of both potential fields can be deduced. Then, the main process of multi-level analysis of oil displacement mechanism of field synergy in the process of heavy oil thermal recovery can be put forward. A practical multi-level case study of typical hot-water flooding displacement can provide useful information and guidance to enhance the displacement process.     

张河湾水库地区断层的ESR年龄测定

本文叙述了电子自旋共振(简称ESR)法所测定的河北省张河湾水库F₁、F₇断层的年龄,将ESR年龄和以往测试的TL年龄进行对比,两种方法测试结果基本吻合,证明ESR测定第四纪断层的可能性,F₁、F₇断层的年龄值均大于定义的活动断层年龄值下限(1.1×104a)。因此,它们不属活动断层,这个结论也被其它地质观测手段所证实。      

基于耦合欧拉-拉格朗日法充灌袋挤淤过程的有限元研究

在含水率大、承载能力低的软土地基上,利用充灌砂袋进行挤淤置换的方法工艺简单、施工方便、处理效果明显,已经广泛地应用在建造围埝和修筑道路中。充灌袋下沉到一定深度后,其重量与地基承载力相等,从而达到极限平衡状态。充灌袋挤淤所达到的深度与其高度存在一定的对应关系,在工程中确定此关系十分重要。通过3组不同宽度的挤淤模型试验,得到充灌袋下沉量与充灌袋高度的曲线关系、淤泥的位移特性及隆起量。利用ABAQUS中耦合欧拉-拉格朗日法（CEL法）,将充灌袋和淤泥分别用拉格朗日体和欧拉体描述,模拟充灌袋挤淤下沉的过程,将模拟得到的充灌袋下沉深度和高度的关系、淤泥的位移特点与试验结果以及理论公式进行对比。结果表明,CEL法模拟得到的结果与试验结果、理论解具有很好的吻合性,说明利用CEL法可以较好地模拟充灌袋的挤淤问题。     

Reverse fault slip through soft rock and sand strata by centrifuge modeling tests

The devastating damage after the 1999 Chi-Chi and 1999 Izmit earthquakes has greatly motivated soil–reverse fault interaction studies. However, most centrifuge modeling studies have employed a single homogeneous soil layer during testing, which does not represent in situ conditions. Indeed, while geological conditions vary spatially, engineering soils are often underlain by soft rocks. Therefore, four centrifuge models were developed to evaluate the effect of soft rock layers on the ground surface and subsurface deformation. Sand–cement mixtures of varying thicknesses with a uniaxial compressive strength of 0.975 MPa, simulating extremely soft rock, were overlain by pluviated sandy soil. The model thickness was 100 mm, corresponding to 8 m in the prototype scale when spun at 80 g. Every model was subjected to a vertical offset of 50 mm/4 m (0.5 H; H: total sedimentary deposit thickness) along a reverse fault with a 60° dip. The results indicate that the presence of a soft rock stratum results in the creation of a horst profile at the ground surface. Additionally, the thinner the soil layer on top of the soft rock stratum is, the longer and higher the horst created at the ground surface. Consequently, the fault deformation zone lengthens proportionally with the increasing thickness ratio of the soft rock. Furthermore, the presence of soft rock as an intermediary stratum between bedrock and soil causes the deformation zone boundary on the hanging wall side to move in the direction of fault movement.

     

A Study on Crack Damage Stress Thresholds of Different Rock Types Based on Uniaxial Compression Tests

When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress σ _cc, crack initiation stress σ _ci, crack damage stress σ _cd, and uniaxial compressive strength σ _ucs; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress σ _cd, its threshold, and a possible relationship between σ _cd and the uniaxial compressive strength. The σ _cd of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in σ _cd /σ _ucs between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average σ _cd /σ _ucs resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on σ _cd /σ _ucs. The ratio σ _cd/σ _ucs could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.     

五十年创业成果丰硕继承伟业再创辉煌--纪念北京矿产地质研究院成立五十周年

52年前,1955年6月18日北京矿产地质研究院宣告成立,开始了创新创业的历程.     

Field investigation of deformation characteristics and stress mobilisation of a soil slope

Stress mobilisation and deformation of a slope are important for engineers to carry out reliable design of retaining systems. However, most case histories reported mainly on the response of pore water pressure (PWP), whereas knowledge about the stress deformation characteristics of slope is limited. In this study, a saprolitic soil slope was instrumented to monitor not only the responses of PWP but also horizontal stress and horizontal displacement. To assist in the interpretation of field data, a series of laboratory tests was conducted to characterise volume change behaviour of the soil taken from the site, under the effects of both net stress and suction. During a rainstorm event when positive PWP built up, a remarkably large displacement of 20 mm was recorded between 5.5- and 6-m depths, and the top 5 m of the slope exhibited translational downslope movement. This caused an increase in Bishop’s effective horizontal stress by 350 %, which reached a peak value close to 40 % of a Bishop’s effective passive stress. During the subsequent dry season when suction was recovered, an upslope rebound of 10 mm was recorded. Comparison of field and laboratory data reveals that the rebound was attributed to suction-induced soil shrinkage. This rebound led to a decrease in the Bishop’s effective horizontal stress previously built up during the storm event.