岩石炮孔预切槽爆破断裂成缝机理研究

应用岩石断裂力学理论和爆生气体膨胀准静压理论，建立了岩石中炮孔不偶合装药孔壁预切槽爆破时的脆性断裂力学模型，分析了裂缝的扩展规律，包括起裂、止裂条件、起裂方向、扩展长度和裂缝扩展过程中的速度变化等。此外，本文还就炮孔预切槽爆破时的动态效应进行了初步探讨。     

A study on the effect of weld groove designs on residual stresses in SS 304LN thick multipass pipe welds

Present research describes the effect of weld groove designs on residual stresses of thick SS 304LN pipe welds which are commonly utilized for applications such as boiling water reactor system, oil and steam piping. The faying surfaces of the pipe joints were machined to generate conventional and narrow groove geometries for welding. Circumferential multipass pipe welding was carried out without applying preheat and post weld heat treatment. Blind hole drilling technique was employed for measuring hoop and axial residual stresses in narrow and conventional grooved SS 304LN pipe welds considering plasticity and stress concentration effects of hole drilling process. The result exhibited 20 to 30 percent reduction in residual stresses in narrow grooved pipe welds. A finite element model was developed for estimating the pass by pass peak temperature distributions in the pipe welds. Sequentially coupled thermomechanical elastic-plastic analysis of both conventional and narrow groove pipe welds indicated close agreement between the predicted and experimentally determined hoop and axial residual stresses.     

Q235厚钢板开孔板和缺口板断裂试验

对10个中心开椭圆孔和10个单侧半椭圆缺口25mm厚板进行了断裂试验,研究了开孔和缺口尖锐度对厚钢板断裂模式的影响。试验结果显示:试件的初始宏观裂纹形成于缺口顶端厚度中面,裂纹在厚度方向贯通后沿垂直加载方向迅速扩展,直至断裂。开孔或缺口愈尖锐的试件,其开裂延性愈差。断口粗糙呈暗灰色且有韧窝,断裂形式为正断与剪断混合型。本次试验为研究结构钢厚板断裂机理及抗断设防提供了较可靠的试验数据。     

超长双预应力混凝土简支梁现场预制台座施工

双预应力混凝土工字梁是最近几年开发出来的简支大跨度桥梁构件。其单梁的高跨比值达1/30,梁长48.4 m,适宜在桥址现场制梁。结合松江花辰路油墩港主桥,着重介绍设置在现场的制梁槽线台座的经验。论述场地的选择、槽线台座的布置、槽线台座关键部位的技术处理。介绍的施工技术可供施工、监理人员借签,也可供大专院校师生参考。     

中等厚度开孔板和缺口板断裂试验

对中等厚度的10个中心开椭圆孔板件和10个单侧半椭圆缺口板件进行断裂试验,研究开孔和缺口尖锐度对中等厚度钢板断裂模式的影响。试验较精确地记录了全程载荷-位移曲线。试验结果显示:试件的第一条宏观裂纹起始于缺口顶端厚度中面,裂纹在厚度方向贯通后沿垂直加载方向迅速扩展,直至完全断裂。开孔或缺口愈尖锐的试件,其开裂延性愈差。开孔板试件宏观断裂荷载比缺口板试件明显要高。断口粗糙且有大量韧窝,断口暗灰色呈杯锥状,断裂形式为正断与剪断混合型。本次试验为研究中等厚度钢板断裂机理及抗断设防提供了较可靠的试验数据。     

开槽垫板工艺对高层钢框架节点脆断性能的影响

介绍了开槽垫板施工工艺的特点 ,并利用有限元法和断裂力学原理对应用开槽垫板的高层钢框架节点的脆断性能进行了分析。和我国目前采用的施工工艺的比较结果表明 ,应用开槽垫板的节点发生脆性断裂的可能性要小得多 ,是一种值得推荐的施工方法。     

Steady temperatures in a wall penetrated by a hole and exposed to fire on one side

A hole in a wall weakens the wall's ability to withstand fire. Key parameters that control the safety of the system are identified through a calculation of the temperatures. To obtain the most severe case, a steady state is assumed. The mass flow rate ?_g through the hole and the thickness ? of the wall are the most important parameters. These may be grouped with the gas viscosity μ_g to form the dimensionless quantity ?_g/?μ_g. When the value of this quantity is near 1, the back face of the wall and the emerging gases are cool. They are dangerously hot when ?_g/?μ_g is near 100.     

Fracture toughness study for a brittle rock subjected to mixed mode I/II loading

A semi-disk specimen containing an angled edge crack has been used in the past for conducting fracture tests on a brittle rock named Johnstone [Fracture testing of a soft rock with semi-circular specimens under three-point bending. Part 2—mixed mode. Int J Rock Mech Min Sci Geomech Abstr 1994b;31(3):199–212]. The test specimen is appropriate for investigating brittle fracture when the rock samples are subjected to the combined effects of tension and shear along the crack line. However, the experimental results reported in Lim, Johnston, Choi, Boland [Fracture testing of a soft rock with semi-circular specimens under three-point bending. Part 2—mixed mode. Int J Rock Mech Min Sci Geomech Abstr 1994b;31(3):199–212.] are inconsistent with all of the well-known theoretical criteria available for predicting mixed mode brittle fracture. In this paper, a modified criterion is used to provide accurate predictions for the reported experimental results. The modified criterion makes use of a three-parameter model (based on K_I, K_II and T) for describing the crack tip stresses. It is shown that the non-singular stress term T has a significant role when the rock fracture tests are conducted on the semi-disk specimens.     

无黏结预应力混凝土开洞板的变形研究

通过对2块不开洞和6块开洞无黏结预应力混凝土板的实验,分析了荷载与挠度的关系,通过实测挠度值与计算值相比较,发现实测值大于计算值,分析其原因,主要是板的结构形式、支承梁、开洞及洞口位置等这些因素对挠度产生了影响。     

模型盾构隧道管片纵缝接头设计方法

考虑到拼装的缩尺模型管片环与原型管片环的纵缝接头刚度相似性难以满足要求,建议缩尺模型隧道采用开槽模型接头,并分别得到了采用两侧同时开槽、内侧开槽及外侧开槽的模型接头设计计算方法。通过开槽模型接头的管片环模型与梁—弹簧模型的计算结果比较,表明开槽模型接头的设计方法可行,开槽模型接头能很好地模拟拼装管片接头。在综合考虑开槽模型接头的开槽宽度对管片环结构内力与变形的影响与开槽模型接头的加工可行性的基础上,建议开槽模型接头对应的管片环中心角取值为3°~5°。提出的开槽模型接头设计计算理论可用于缩尺模型管片环的纵缝接头设计及在惯用法均质圆环的基础上进行局部抗弯刚度折减的数值模型隧道的建模。     

Elastic stability of bi-axially loaded rectangular plates with a single circular hole

The finite-element method has been employed to determine the elastic buckling stresses of a bi-axially loaded perforated rectangular plate with dimensions a and b in the x- and y-directions, respectively. The considered perforation is a single circular hole whose center is located along the longitudinal axis of the plate. The considered plate has simply supported edges in the out-of-plane direction and is subjected to bi-axial uniformly distributed end loads (compressive load σ_x in the x-direction, and compressive or tensile load σ_y in the y-direction). Parameters considered in the study are the plate's aspect ratio a/b, the stress ratio ξ between the applied stresses in the y- and x-directions (ξ=σ_y/σ_x), the circular hole size d and location e_x.The study shows that, in most of the considered cases, the bigger the hole size d, the lesser the plate stability and the lesser the buckling stresses. It also shows that the plate aspect ratios, a/b, between 0.6 and 1.2 should be avoided for plates with large holes and negative ξ, due to the large reduction in the buckling stresses. The hole location should also be selected to be away from the loaded edge of the plate as much as possible (better to have e_x/b>1.0) to increase the buckling stresses and improve stability. The study demonstrates also that the increase in tension in the y-direction in bi-axially loaded plate with large hole (d/b>0.4) reduces its stability. This is in contrary to the expected increase in the stability due to the increase in tension which can be seen clearly in the cases of solid plates and plates with small holes.     

Surface pressure distribution on patterned cylinders under simulated atmospheric boundary layer winds

Extensive research has been previously conducted on pressure distribution of cylindrical models under uniform and laminar flow conditions. However, typical civil structures such as high‐rise buildings or towers are under the atmospheric boundary layer (ABL) conditions. Knowing this, the present research aims to quantify the effectiveness of surface patterns in reducing the suction zone under a simulated ABL condition. Two different surface patterns, U‐grooved and V‐grooved, were selected to be tested in wind tunnel. In addition to patterned cylinders, tests were also conducted on a smooth‐surfaced cylinder, serving as the control of the experiment. An array of roughness elements was placed at the upstream end of the test section with the purpose of inducing ABL winds within the test section. Without the ABL wind, the cylinder covered in V‐grooved riblets was most effective in reducing the suction zone followed by the U‐grooved cylinder. With the simulated ABL condition, V‐grooved cylinder continued to show decreased suction although the amount of decrease was less. Both grooved cylinders showed decreased peak pressure coefficients under the ABL condition compared to the non‐ABL condition.     

甘肃龙首山成矿带绿草沟断裂地电结构特征及铀成矿作用分析

文章通过对龙首山铀成矿带的主要控矿构造——绿草沟断裂(F3)进行音频大地电磁测量,研究了该断裂电性结构,结合区内地质情况与0号勘探线地质剖面资料进行对比分析,推断了断裂的位置、产状以及深部延伸特征。总结了绿草沟断裂矿化电性特征,主要表现为线性视电阻率异常低阻带,近东西走向,倾向北。预测L02线绿草沟断裂与次级断裂深部交汇部位,可以作为下一步找矿工作的重点区。     

孔深影响爆炸应力波特性的数值分析

炮孔深度（装药长度）是影响岩体中爆炸应力波特性的因素之一。利用所编制的有限差分程序SMMIC计算了单自由面条件下，垂直炮孔爆炸应力波的传播过程。计算表明，炮孔深度（装药长度）增大，爆炸应力波峰值随距离的衰减指数减小。在算例中，4m和2m也深的爆炸应力波峰值随距离的衰减指数分别为1．35和1．56。     

切槽式钢套管混凝土柱的原理与应用

在传统的钢套管混凝土柱的基础上提出了一种改进的切槽式钢套管混凝土柱,研究分析结果表明,切槽式钢套管混凝土柱用于既有结构的加固或用作现浇结构的基本构件都是方便可行的,在实际工程中利用卷制钢板简单焊接形成的钢套管混凝土柱代替普通的钢管混凝土柱是合理可行的,并有很高的实用价值和经济价值。     

The nature and behavior of gases in natural waters

During the past two years tests have been carried out to determine the nature and behavior of dissolved gases in natural waters from a variety of different environments. The environments tested include surface stream and lake waters, ground waters from wells and springs, and drill hole waters from uranium and copper deposits. Close to 800 water samples have been analysed to date for the following gases: H₂, He, CH₄, Ne, N₂, O₂, H₂S, Ar, CO₂ and Rn. The first nine were determined using a mass spectrometric method with an average sampling and analytical precision of about 20%. Rn was determined with similar precision using silver-activated ZnS counters.The gases of interest from the viewpoint of biochemical and geochemical activity were found to be H₂, He, CH₄, O₂, H₂S, CO₂ and Rn. Ne, N₂ and Ar revealed no clearly recognizable patterns of dispersion.The composition of the dissolved gases from the sampled environments varied over a wide range. Generally speaking, the occurrence of specific gases in specific environments could usually be interpreted in terms of the known geochemistry of the environment. The presence of He anomalies was most difficult to explain. Its chemical inertness and related high geochemical mobility permit He to travel great distances from its source. He and Rn were always present in all environments tested. Gases in surface waters contained, as a rule, only equilibrium amounts of He. In waters near U deposites a positive correlation between He and Rn was observed.     

钻孔夯密桩技术在高层建筑盐渍土地基处理中的应用

本文介绍了西宁市某住宅小区高层建筑盐渍土地基处理方案的设计以及钻孔夯密桩的施工概况和处理效果,并对黄土状盐渍土地基设计与施工中的几个问题进行了分析。     

无粘结预应力开洞平板的配筋形式探讨

探讨了无粘结预应力开洞平板中的布筋形式。通过有限元法求得中心开洞板和偏心开洞板在 4种常见的布筋形式下使用阶段的挠度和应力 ,结果表明 ,两边均匀布筋和两边都分别在柱上板带和洞口板带集中布筋两种形式在使用阶段具有几乎同样好的结构性能 ,所以建议在相似的预应力平板开洞工程中采用两边都分别在柱上板带和洞口板带集中布筋形式。对于洞口的选择也提出了建议     

φ1600mm金刚石圆锯片的有限元分析

本文采用有限单元法对金刚石锯片应力及振动进行了系统的分析,并找出其一般规律。     

岩体间隔破裂机制及演化规律初探

 在地壳岩层或岩土工程结构中,有一个非常重要的破裂现象,即间隔破裂现象,其形成机制到目前仍不十分清楚。这些现象包括地层中的等间距破裂、大地干裂(龟裂)以及深部巷道围岩中的间隔破裂(分区破裂)等。此外,混凝土结构中的间隔裂纹、陶瓷表面因冷缩产生的龟裂等,都是间隔破裂现象的典型例子。以此为背景,介绍通过RFPA数值试验方法研究间隔破裂机制和演化规律的初步结果,包括：(1) 条状间隔破裂(平行破裂);(2) 网状间隔破裂(龟裂);(3) 环状间隔破裂(分区破裂)。