振动沉管碎石桩复合地基综合检测若干值得研究的岩土工程问题

近年来,振动沉管碎石挤密桩在处理饱和黄土地基方面得到了相当广泛的应用。本文通过对西安市某工程振动沉管碎石桩复合地基的综合检测,提出几个值得研究的岩土工程问题。     

Response of rigid piles during passive dragging

This paper develops a three‐layer model and elastic solutions to capture nonlinear response of rigid, passive piles in sliding soil. Elastic solutions are obtained for an equivalent force per unit length p_s of the soil movement. They are repeated for a series of linearly increasing p_s (with depth) to yield the nonlinear response. The parameters underpinning the model are determined against pertinent numerical solutions and model tests on passive free‐head and capped piles. The solutions are presented in non‐dimensional charts and elaborated through three examples. The study reveals the following:

• On‐pile pressure in rotationally restrained, sliding layer reduces by a factor α, which resembles the p‐multiplier for a laterally loaded, capped pile, but for its increase with vertical loading (embankment surcharge), and stiffness of underlying stiff layer: α = 0.25 and 0.6 for a shallow, translating and rotating piles, respectively; α = 0.33–0.5 and 0.8–1.3 for a slide overlying a stiff layer concerning a uniform and a linearly increasing pressure, respectively; and α = 0.5–0.72 for moving clay under embankment loading.
• Ultimate state is well defined using the ratio of passive earth pressure coefficient over that of active earth pressure. The subgrade modulus for a large soil movement may be scaled from model tests.
• The normalised rotational stiffness is equal to 0.1–0.15 for the capped piles, which increases the pile displacement with depth.

The three‐layer model solutions well predict nonlinear response of capped piles subjected to passive loading, which may be used for pertinent design. Copyright © 2016 John Wiley & Sons, Ltd.     

直墙前矩形月池水波振荡研究分析

月池内流体存在活塞和晃荡两类振荡现象。基于线性势流理论,推导了波浪斜向入射下,直墙前矩形月池辐射和绕射问题的解析解。通过分离变量法和特征函数展开法求解了速度势函数,根据边界条件来确定速度势函数中的未知系数,由速度势函数计算斜向波与矩形月池相互作用的水动力系数和波浪激励力,对它们的变化规律进行了分析讨论,研究了底部开口大小、波浪入射角度对矩形月池水动力特性的影响以及直墙远近对波浪力的影响。结果表明,月池底部开口大小对流体水平作用的影响较小,而对流体垂直作用的影响较大;波浪入射角度的变化对矩形月池横荡和横摇运动时的水动力特性有一定的影响;在一定条件下,直墙的存在会使得月池在水平方向所受到的波浪力比开敞水域中的要大。     

基于高斯投影的矩形图廓算法及实现

大比例尺地图通常采用高斯-克吕格投影,标准分幅的地图图廓呈近似梯形。在应用中,一些专题地图,特别是专题地图集要求图廓为矩形,针对该需求,本文提出了一种高斯投影下地图矩形图廓坐标的计算方法,解决了矩形图廓不易计算的问题。实践证明,该方法能够满足精度需求,在专题地图制图中具有一定的价值。     

两层流体中矩形箱浮体的附加质量和阻尼系数

研究了两层流体中矩形箱浮体的辐射问题。基于特征函数匹配理论,针对矩形箱浮体的三种振荡运动模式(横荡、垂荡和横摇),建立两层流体中矩形箱浮体辐射势的求解方法,导出矩形箱浮体附加质量和阻尼系数的计算公式。对所建立的求解模型进行了数值计算分析,结果表明在矩形箱浮体的某个振荡频率范围内,流体的分层效应对其附加质量和阻尼系数有显著影响的。     

潮间带垒石蒙网养鲍技术研究

在潮间带进行垒石蒙网养鲍试验，４个岩礁区共设置１３６个石垛，放养壳长１．３￣３．０厘米的鲍５５．１万只，经１８个月养殖，共产商品鲍１９．２５４吨，平均亩产１３９７．８公斤，平均壳长６．８１厘米，成活率８９．６％，实现产值６９３．１４４万元，利润３５２．８１万元。该成果１９９６年被评为青岛市科技进步三等奖。     

海水中近60年钢板桩的腐蚀状况

对码头入海近60年钢板桩进行研究。采用水下摄像、水下超声波测厚、水下切割取样等手段调查和检测钢桩腐蚀状况，结果表明钢板桩厚度减薄较小，腐蚀较轻。钢板桩的材质成份值得借鉴。     

Suppression of Wave-Excited Vibration of Offshore Platform by Use of Tuned Liquid Dampers

This paper describes experimenlal and theoretical investigations of Tuned Liquid Damper (TLD) characteristics tor suppressing the wave-excited structural vibration. The structural model lor the experiments is scaled according to a full size offshore platform by matching their dynamic properties. Rectangular TLDs of different sizes with partially filled liquid are examined. By observing the performance and behavior of TLDs through laboratory experiments, the study investigates the influence of a number of parameters, including container size, container shape, frequency ratio, and incident wave characteristics. In an analytical study, a mathematical model that describes the nonlinear behavior of liquid in TLD and the interaction of TLD and structure is prerequisite. The validity of the model is evaluated and simulating results can reasonably match the corresponding experimental results.     

Vertical uplift resistance of close-spaced shallow rectangular group anchor plates embedded in sand

Abstract

This study describes an analytical solution for determining the ultimate vertical uplift resistance of a group of two and multiple number of close-spaced shallow rectangular anchor plates embedded horizontally in sand. The analysis was performed by using an upper bound theorem of limit analysis with the employment of the kinematically admissible three-dimensional (3D) rigid wedge collapse mechanisms. Results are obtained in terms of dimensionless uplift factors F_γ and F_q due to the components of soil self-weight and surcharge pressure acting on the ground surface for a wide range of parameters. It was found that the magnitude of uplift factors decreases substantially with a decrease in the clear spacing between the anchors, soil friction angle, and embedment ratio, and an increase in the aspect ratio of anchors. Further, it was noticed that when the clear spacing between the anchors is greater than or equal to the certain critical value, the interaction effect of anchors vanishes and the magnitude of uplift factors associated with a group of anchors becomes equal to that of single isolated anchors. The present solutions are found to compare reasonably well with those theoretical, numerical, and experimental results available in the literature.     

基坑水泥搅拌桩帷幕止水施工质量控制

基坑止水,对基坑(特别是深基坑)开挖及地下结构施工至关重要。根据多年的工程施工实践,总结和分析用于基坑开挖止水的水泥搅拌桩施工工艺流程和质量控制方面的有关问题。