Modelling the flow of self‐compacting concrete     

S. Kulasegaram  B. L. Karihaloo  A. Ghanbari 《国际地质力学数值与分析法杂志》2011,35(6):713-723

A Lagrangian particle‐based method, smooth particle hydrodynamics (SPH), is used in this paper to model the flow of self‐compacting concretes (SCC) with or without short steel fibres. An incompressible SPH method is presented to simulate the flow of such non‐Newtonian fluids whose behaviour is described by a Bingham‐type model, in which the kink in the shear stress vs shear strain rate diagram is first appropriately smoothed out. The viscosity of the SCC is predicted from the measured viscosity of the paste using micromechanical models in which the second phase aggregates are treated as rigid spheres and the short steel fibres as slender rigid bodies. The basic equations solved in the SPH are the incompressible mass conservation and Navier–Stokes equations. The solution procedure uses prediction–correction fractional steps with the temporal velocity field integrated forward in time without enforcing incompressibility in the prediction step. The resulting temporal velocity field is then implicitly projected on to a divergence‐free space to satisfy incompressibility through a pressure Poisson equation derived from an approximate pressure projection. The results of the numerical simulation are benchmarked against actual slump tests carried out in the laboratory. The numerical results are in excellent agreement with test results, thus demonstrating the capability of SPH and a proper rheological model to predict SCC flow and mould‐filling behaviour. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Review and enhancement of 3D concrete models for large‐scale numerical simulations of concrete structures     

B. Valentini  G. Hofstetter 《国际地质力学数值与分析法杂志》2013,37(3):221-246

The present paper focuses on selected plasticity and damage‐plasticity models for describing the 3D material behavior of concrete. In particular, a plasticity model and a damage‐plasticity model are reviewed and evaluated. Based on the results of the evaluation, enhancements are proposed, aiming at improving the correspondence between predicted and observed material behavior and aiming at implementing a robust and efficient stress update algorithm in a finite element program for performing large‐scale 3D numerical simulations of concrete structures. The capabilities of the concrete models are demonstrated by 3D numerical simulations of benchmark tests with combined bending and torsional loading and combined compression and shear loading and by a large‐scale 3D finite element analysis of a model test of a concrete arch dam. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

混凝土灌注桩桩头渗水的处理及预防措施          下载免费PDF全文

孙立宝 《探矿工程》2016,43(5):86-88

混凝土灌注桩桩头渗水对桩体混凝土受力和基底防水产生影响,对混凝土结构中的钢筋造成腐蚀。结合工程实例,对桩头渗水产生的原因进行分析,主要有操作经验不足、责任心不强,灌注器具不合格,混凝土质量指标不符合要求,灌注接近结束时拔管速度过快、灌注终了超灌高度测量不准,基土含水量高、水压大等;出现桩头渗水可采用人工剔除或注浆封堵处理;介绍了预防措施,包括加强作业人员培训,强化灌注器具检查,严控混凝土质量,重点监管终灌时的状态,做好基坑内降水工作等。  相似文献   

全珊瑚骨料海水混凝土力学性能试验研究   总被引：3，自引：1，他引：2  

糜人杰  余红发  麻海燕  达波  袁银峰  张小平  朱海威  窦雪梅 《海洋工程》2016,34(4):47-54

为了探讨全珊瑚骨料海水混凝土的基本力学性能,并比较其与普通混凝土和轻集料混凝土的差异,通过实验系统测定了珊瑚混凝土的基本力学性能,建立了其轴心抗压强度(f_(c,m))、劈裂抗拉强度(f_(sp,m))、抗折强度(f_(t,m))与立方体抗压强度(f_(cu,m))之间的线性关系与计算公式。结果表明:在强度等级C20~C50的范围内,珊瑚混凝土的f_(c,m)和f_(sp,m)分别比普通混凝土的f_(c,m)和f_(sp,m)高出10%~48%和9%~33%,随着强度等级的提高,两种混凝土之间的差距在减小。珊瑚混凝土的f_(t,m)与普通混凝土的ft,m之间的差异规律与强度等级有关,较低强度等级的C30珊瑚混凝土ft,m比普通混凝土的f_(t,m)要高4%,而较高强度等级的C55珊瑚混凝土f_(t,m)比普通混凝土的f_(t,m)低13%。较高强度等级的C50珊瑚混凝土f_(c,m)、f_(sp,m)和f_(t,m)分别比页岩陶粒轻集料混凝土的f_(c,m)、f_(sp,m)和f_(t,m)低11%、0.9%和4%。  相似文献   

The Effect of Concrete Deformation on Displacement of an Axially Loaded Drilled Shaft     

Dongwook Kim  Hobi Kim  Kyung Joon Shin 《Marine Georesources & Geotechnology》2016,34(2):116-126

This article presents the settlement of drilled shafts resulting from their structural deformations. Although drilled shafts are widely used as foundations for settlement-sensitive structures such as bridges and high-rise buildings, the structural deformations of drilled shafts are not typically taken into account in the design process. However, if unexpected structural deformations of drilled shafts cause additional settlement to the foundation, the serviceability of the superstructure can be jeopardized. Unfortunately, very few research efforts have been made to quantify the structural deformation of drilled shafts; this needs to be addressed to accurately predict the settlement of drilled shafts. In this study, we investigate the effect of structural deformation on displacement of axially loaded drilled shafts. Finite element analyses were performed to quantify the structural deformation of drilled shafts. The analysis results indicated that the structural deformation of drilled shafts could be quite significant for long drilled shafts. The main factors that affected the structural deformation of drilled shafts were found to be pile length, the material properties of drilled shafts, and the relative humidity of surrounding soil. An approximate equation is proposed to estimate the long-term deformation of drilled shafts.  相似文献   

软岩隧道中双层初期支护的应力情况分析     

姚正源 《探矿工程》2018,45(7):73-76

两水隧道穿越的地层主要岩性为炭质千枚岩,地质情况较差,围岩破碎度高,节理发育。自2009年两水隧道开工建设以来,隧道工程问题层出不穷,出现了初期支护开裂、破坏,甚至出现二衬开裂、掉块,仰拱隆起等严重的隧道结构破坏现象,施工进度缓慢。在进口桩号为DK359+712～ DK359+742段采用双层初期支护和单层二次衬砌的支护方式,取得了良好的效果。通过应力情况分析为炭质千枚岩隧道的支护选型提供了依据。  相似文献   

Study of bond stress–slip relationship and radial dilation in prestressed concrete     

José Mª Benítez  J.C. Gálvez  M.J. Casati 《国际地质力学数值与分析法杂志》2013,37(16):2706-2726

This paper presents two test procedures for evaluating the bond stress–slip and the slip–radial dilation relationships when the prestressing force is transmitted by releasing the steel (wire or strand) in precast prestressed elements. The bond stress–slip relationship is obtained with short length specimens, to guarantee uniform bond stress, for three depths of the wire indentation (shallow, medium and deep). An analytical model for bond stress–slip relationship is proposed and compared with the experimental results. The model is also compared with the experimental results of other researchers. Since numerical models for studying bond‐splitting problems in prestressed concrete require experimental data about dilatancy angle (radial dilation), a test procedure is proposed to evaluate these parameters. The obtained values of the radial dilation are compared with the prior estimated by numerical modelling and good agreement is reached. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

粉煤灰碎石混凝土灌注桩法加固软弱地基效果的分析与检验   总被引：1，自引：0，他引：1  

龚有满 《水文地质工程地质》1993,20(5):13-17,9

对由深厚软弱土层组成的地基,采用粉煤灰碎石混凝土灌注桩法予以加固处理时,其施工机具相对简单,工期短,节约“三材”,投资省,具有显著的经济效益。由粉煤灰碎石混凝土灌注桩和深厚软弱土层共同构成的复合地基的工程特性,介于一般碎石桩复合地基与混凝土桩桩基之间,其基本特征是:承载力的提高,主要是置于深厚软弱土层中的粉煤灰碎石混凝土灌注桩的排水和垂直加筋作用的结果;其承载机理,部分具有一般碎石桩复合地基的特征;在结构物荷载作用下,其桩、土荷载分担特征,比较接近于普通混凝土桩桩基。  相似文献   

泥湾门大桥浅海大直径嵌岩桩施工技术          下载免费PDF全文

柴云来 《探矿工程》1994,(3):28-29,31

介绍了在浅海施工直径２．２０ｍ嵌岩桩的技术问题。包括平台的搭设，用刮刀钻头与牙轮钻头钻进克取硬岩一次成孔工艺，利用冲洗液平衡原理处理浅海钻进护简断裂的成孔方法，改进浇灌清孔流程，保证浇灌质量。  相似文献   

浅埋软弱地层隧道旋喷预衬砌支护技术的研究   总被引：3，自引：0，他引：3       下载免费PDF全文

李远宁  段玉刚吴胜 《探矿工程》2001,(5):58-61

论述了浅埋软弱地层隧道旋喷预衬砌支护的研究背景及国内外研究现状、室内试验、旋喷器具、施工工艺及应用情况,并与其它施工方法进行了对比,效益显著。  相似文献