控温控光培育长江系中华绒赘蟹“早豆蟹”的研究

在早春利用水泥池塑料大棚,采取控温控光,充气、移植水草（喜旱莲子草）、控制水质及合理投饵等强化培育技术,将长江水系中华绒整蟹大眼幼体培育成“早豆蟹”,使蟹苗当年养成商品蟹,改革河蟹两年养成的传统生产模式。经过两年的研究,在1287．2m2试验池中共培育出“早豆蟹”183万只,平均每平方米700多只。成活率达60％,投入产出比为1：2．5,经济效益显著。     

Experimental study on the electrical resistivity of soil–cement admixtures

Recently in China, soil–cement is widely used to improve the soft ground in the highway construction engineering. Literature studies are mainly investigating the mechanical properties of the soil–cement, while its properties of the electrical resistivity are not well addressed. In this paper, the properties of the electrical resistivity of the reconstituted soil-cement and the in situ soil–cement columns are investigated. The test results show that the electrical resistivity of the soil–cement increases with the increase in the cement-mixing ratio and curing time, whereas it decreases with the increase in the water content, degree of saturation and water–cement ratio. A simple equation is proposed to predict the electrical resistivity of soil–cement under the condition of the specified curing time and water–cement ratio. It is found that the electrical resistivity has a good relationship with the unconfined compression strength and blow count of SPT. It is expected that the electrical resistivity method can be widely used for checking/controlling the quality of soil–cement in practice.     

水泥配料集散式控制系统

介绍以16位单片机8096为核心的集散式水泥配料自动控制系统的硬件电路结构和工作原理以及软件设计方法，给 出了部分单元电路及其结构参数。实际应用表明，该系统控制效果良好，可靠性高，取得了较好的社会效益和经济效益。     

Characterization of frozen soil-cement mixture for berm construction in cold regions

Lagoon berms in western Alaska are difficult to design and build due to limited resources, high cost of construction and materials, and warm permafrost conditions. This paper explores methods to treat locally available frozen materials and use them for berm construction. The goal is to find an optimized mix ratio for cement and additives that can be effective in increasing the strength and decreasing the thaw settlement of an ice-rich frozen silty soil. Soil of similar type and ice content to the permafrost found at a project site in Eek, Alaska is prepared in a cold room. The frozen soil is pulverized and cement, additives and fibers are added to the samples for enhancing shear strength and controlling thaw settlement. Thaw settlement and direct shear testsare performed to assess strength and settlement characteristics. This paper presents a sample preparation method, data from thaw settlement and direct shear tests, and analyses of the test results and preliminary conclusions.     

注浆技术在洛湛铁路岩溶路基施工中的应用

洛湛铁路D1K41+300~84585段路基上部土层松散，下部岩体(石灰岩)溶洞发育，根据工程地质水文地质情况，确定注浆参数和注浆方式，在土体和岩体中通过不同的浆液注浆，固结、充填松散的土层和岩体中的溶蚀、溶洞、溶槽等，使之形成完整的固结体，从而加强岩溶路基的承载力，确保铁路正常运营。介绍了注浆施工工艺及注浆效果。     

Remanent Magnetization in Portland-Cement-Based Materials

The purpose of this research is to demonstrate the possibility of applying one geophysical method to studying untraditional systems as is the case with Portland-cement-based materials. The research demonstrates how conventional paleomagnetic methodology can be employed in studying the mode of magnetic recording in present-day industrial materials. Portland-cement admixtures such as fly ashes and furnace slags should be discriminated, because those particles interact in soils and sediments in nature. Moreover, a better undertanding of magnetic remanent acquisition in model materials can serve to improve the interpretation of magnetic remanent acquisition in natural rocks formed a long time ago. The magnetic constituents of Portland-cement paste and mortar acquire a magnetic remanence due to their alignment with the earth's magnetic field at the casting place. This magnetization can be measured using ordinary paleomagnetic techniques. The alignment of the individual magnetic particles accounts for the intensity of the magnetic remanence, which can be increased by adding water and by vibration before setting and hardening. Blast furnace slag admixtures also add to the enhancement of the intensity of remanence. The magnetization of Portland-cement-based materials shows a near linear relationship with the water /cement (w/c) ratios employed in the experimental work; the w/c ratios range between 0.2 – 0.6 in pastes and 0.3 – 0.6 in mortar. Stable remanent magnetization was obtained during the first seven days of setting and hardening, a period necessary for magnetic particles to become locked parallel to the earth's magnetic field. The stability of magnetic remanence predicts the usefulness of the methodology in studying the properties of Portland cement and particularly in the control of iron-bearing admixtures.     

Influence of cap size and strength on settlements of TDM-piled embankments over soft ground

Abstract

This study investigates the impact of pile cap size, soft layer thickness and pile strength on load transfer and settlement behaviors of embankments supported by floating and fixed T-shaped deep cement mixing piles and conventional DCM piles under volume control. Preliminary investigation is performed by a series of small-scale physical model tests. The results reveal that the differential settlement can be substantially reduced with an enlarging pile cap as a result of larger embankment load transferred to the piles. The extended numerical analysis results demonstrate that the pile efficacy is related to the individual pile bearing capacity, which, in turn, depends on the pile cap size. The soft layer thickness has an insignificant effect on differential settlement but a significant effect on average settlement, while the pile strength plays an important role in differential settlement only when the cap size is not very large. Shape factor of at least 3.0 is recommended to ensure the reduction in differential settlement and minimize the effect of the change in pile strength.     

水泥砂浆面层加固砌体墙抗震可靠指标研究

采用水泥砂浆面层加固方法加固砌体房屋是一种简单有效的方法。对比分析了《砌体结构加固设计规范》(GB 50702-2011)^[3]和《建筑抗震加固技术规程》(JGJ 116-2009)^[4]中钢筋网水泥砂浆面层加固砌体墙的可靠性;对10片未加固低强度砖墙和20片单面钢筋网水泥砂浆面层加固低强度砖墙进行拟静力试验,分析了未加固和加固墙体的破坏模式和机理,并提出了适用于钢筋网水泥砂浆面层加固砌体墙的抗震验算公式。研究表明：两标准的可靠水平差别较大,实际应用时,易产生矛盾;未加固墙主要发生沿阶梯形斜裂缝受剪破坏,加固墙主要发生沿通缝受剪破坏和沿阶梯形斜裂缝受剪破坏;建议公式的计算值与试验值吻合良好,未加固墙抗震可靠指标为2.2,加固墙抗震可靠指标为2.5～3.1;砂浆面层加固砌体结构可以显著提高结构的抗震性能。     

黄土−砂浆块界面剪切特性试验及本构模型研究

构筑物与土体接触面力学行为是岩土工程研究的热点之一。基于一系列直剪试验,研究不同法向压力、土体含水率条件下黄土?水泥砂浆块界面剪切特性。结果表明,(1) 在土体含水率为9.2和13.1%条件下,法向压力为50、100 kPa时黄土?沙浆块界面剪切应力?位移曲线表现为应变软化型,且可分为峰值前、峰值后及残余阶段三部分,在法向压力为200、300 kPa时表现为应变硬化型;在土体含水率为17.1、20.8%条件下,不同法向压力时黄土?砂浆块界面剪切应力?位移曲线均为应变硬化型;(2) 黄土?砂浆块界面的抗剪强度包络线符合摩尔?库仑准则,随着含水率的增大,界面黏聚强度降低显著,摩擦强度略有增加,整体抗剪强度降低。当土体含水率由9.2%增加至20.8%时,界面黏聚力由41.5 kPa下降至3.6 kPa,界面摩擦系数由0.50增大至0.58。用非线性模型对界面剪切应力?位移曲线关系进行拟合,结果表明非线性模型可较好反映黄土?砂浆块界面的剪切特性。     

Concrete sulfate corrosion coupled with hydraulic pressure

Abstract

A type of sealed steel box was designed to simulate sulfate attack and hydraulic pressure on concrete. Cup-shaped concrete specimens with water/cement (w/c) ratios of 0.4, 0.5, and 0.6 were fabricated. During the 270 days corrosion time, corrosion behavior on concrete surfaces was observed every 30 days. The extent of damage on concrete was calculated on the basis of the results of periodic ultrasonic testing. After the completion of experiments, X-ray fluorescence analysis was conducted on the element contents at different depth locations of partial specimens. Experimental results showed that hydraulic pressure accelerated the sulfate attack on concrete, and high pressure yielded serious damage. In comparison with zero pressure, the accelerating coefficients of 0.1, 0.2, and 0.3?MPa hydraulic pressures were 1.48, 1.75, and 2.35, respectively. Hydraulic sulfate corrosion can bring additional sulfate ions into concrete and cause chemical and physical sulfate corrosions on concrete simultaneously, thereby resulting in serious damage on concrete. The reduction of w/c ratio and incorporation of fly ash are beneficial for concrete to resist hydraulic sulfate attack.