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Load capacity evaluation of different typologies of short and small diameter piles 不同类型短桩和小直径桩的承载力评价
IF 0.5 Pub Date : 2023-07-10 DOI: 10.28927/sr.2023.004722
G. Masutti, Patrícia Falcão, M. Baroni, R. Barbosa, T. Souza
It is common to observe residences with a high number of pathologies related to differential settlements in the municipality of Cruz Alta, Rio Grande do Sul, Brazil. Motivated by this perspective the first Geotechnical Engineering Experimental Field was implemented in the municipality. Standard penetration test and cone penetration test was conducted to characterize the subsoil and execute 17 excavated piles: nine compression piles and eight reaction piles. This technical note presents and discusses the results of the geotechnical load capacity obtained with the static load test in three different pile conditions: conventional piles, floating piles, and reinforced piles by inserting a crushed stone layer compacted at the bottom of the drilling. The piles evaluated have a length of 3 m and a diameter of 30 cm. The piles are immersed in a layer of unsaturated laterite soil. Conventional piles are extensively executed in the municipality due to the limited equipment of the companies offering this service. In summary, the piles presented low bearing capacity, however, the reinforced piles proved to be a viable alternative in terms of increased resistance. The conventional piles presented low load capacity and significant settlements. The insertion of the reinforcement at the tip of the pile resulted in a resistance gain in the range of 31%. The study of floating piles was important to understand the behavior of the pile base. This technical note will enable the geotechnical understanding for future researchers or designers who will work with this soil condition in the state of Rio Grande do Sul, Brazil.
在巴西南里奥格兰德州克鲁兹-阿尔塔市,经常观察到患有大量与差异定居点有关的疾病的住宅。基于这一观点,在该市实施了第一个岩土工程试验场。进行了标准贯入试验和圆锥贯入试验,以确定底土的特征,并执行了17根开挖桩:9根压缩桩和8根反作用桩。本技术说明介绍并讨论了在三种不同的桩条件下通过静载试验获得的岩土承载力结果:常规桩、浮桩和在钻孔底部插入压实碎石层的加固桩。评估的桩长3m,直径30cm。桩浸入一层不饱和红土中。由于提供这项服务的公司设备有限,传统桩在该市广泛使用。总之,桩的承载力较低,但事实证明,就增加阻力而言,加固桩是一种可行的替代方案。传统桩承载力低,沉降显著。在桩端插入钢筋导致阻力增益在31%的范围内。对浮桩的研究对于了解桩基的性能具有重要意义。本技术说明将使未来的研究人员或设计师能够了解巴西南里奥格兰德州的土壤条件。
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引用次数: 0
Dosage method for unconfined strength and fatigue life of fiber-reinforced cement-treated sand 纤维水泥处理砂无侧限强度和疲劳寿命的掺量方法
IF 0.5 Pub Date : 2023-07-10 DOI: 10.28927/sr.2023.007322
H. Borges, M. Secco, G. Bruschi, L. Festugato
Fiber-reinforcement has been reported as an effective and cost-attractive technique to improve the mechanical behavior of cemented soils. However, the dosage methodologies for these mixtures are still limited, especially regarding dynamic loading. The objective of this research was to analyze the dynamic response and strength behavior of fiber-reinforced cement-treated sand. In this sense, fatigue life, unconfined compressive strength, and split tensile strength tests were conducted. Results indicated that the mechanical behavior of the soil-cement mixtures was governed by fiber content, cement content and void ratio. The presence of fibers, the increase in cement content and the decrease in void ratio improved the overall mechanical behavior of all specimens. The porosity/cement content index resulted in a viable dosage method to predict both the monotonic and cyclic behavior of the mixtures. Lastly, the statistical analysis of variance corroborated the experimentally observed findings.
据报道,纤维增强是一种有效且具有成本吸引力的技术,可以改善水泥土的力学性能。然而,这些混合物的剂量方法仍然是有限的,特别是关于动态负载。本研究的目的是分析纤维增强水泥处理砂的动力响应和强度行为。从这个意义上讲,进行了疲劳寿命、无侧限抗压强度和劈拉强度试验。结果表明,水泥土混合料的力学性能受纤维含量、水泥含量和空隙率的影响。纤维的存在、水泥含量的增加和空隙率的降低改善了所有试样的整体力学性能。孔隙率/水泥含量指数为预测混合物的单调和循环行为提供了一种可行的剂量方法。最后,方差的统计分析证实了实验观察到的结果。
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引用次数: 0
Design of agglomerates using Weibull distribution to simulate crushable particles in the discrete element method 离散元法中使用威布尔分布模拟可压碎颗粒的团聚体设计
IF 0.5 Pub Date : 2023-07-08 DOI: 10.28927/sr.2023.004922
Bruna Tedesco, M. C. Cordão Neto, M. Farias, A. Tarantino
This paper focuses on the use of the agglomerate technique to simulate crushable particles in the Discrete Element Method. A novel approach is proposed to design a Weibullian agglomerate by mimicking flaws within the crushable particle. The particle is designed with a constant number of sub-spheres in contrast to the approach widely used in the literature. However, the adhesion bonds between sub-spheres within the particle are selected randomly from a normal distribution. The normal distribution is designed to generate negative adhesion values, which are replaced by zero adhesion to mimic flaws within the particle. It is shown that the particle designed in this fashion exhibits a tensile strength that follows the Weibull probability function. This includes the effect of particle size that is remarkably captured quantitatively. Finally, a simple method is proposed to derive the parameters of the adhesion normal distribution from the Weibull parameters determined experimentally on single particle diametral compression tests.
本文的重点是在离散元法中使用团聚技术来模拟可压碎颗粒。提出了一种通过模拟可压碎颗粒内的缺陷来设计Weiburlian团聚体的新方法。与文献中广泛使用的方法相反,粒子设计有恒定数量的子球体。然而,粒子内的子球体之间的粘附键是从正态分布中随机选择的。正态分布被设计为产生负粘附值,该值被零粘附取代,以模拟颗粒内的缺陷。结果表明,以这种方式设计的颗粒表现出遵循威布尔概率函数的拉伸强度。这包括颗粒大小的影响,颗粒大小被显著地定量捕获。最后,提出了一种简单的方法,从单颗粒径向压缩试验中实验确定的威布尔参数推导出粘附正态分布的参数。
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引用次数: 0
Technical feasibility analysis of using phosphogypsum, bentonite and lateritic soil mixtures in hydraulic barriers 磷石膏、膨润土和红土混合土用于水力屏障的技术可行性分析
IF 0.5 Pub Date : 2023-06-27 DOI: 10.28927/sr.2023.009622
Yago Borges, Bismarck Oliveira, M. Boscov, M. Mascarenha
Every year, millions of tons of phosphogypsum, a by-product of the fertilizer industry, are produced worldwide. As just a small part of this amount is reused, this study analyzed a new alternative to reuse this material in geotechnical works, in mixtures with lateritic soil and bentonite for the construction of liners for sanitary landfills. Four compositions were tested: 100% soil, 10% phosphogypsum + 90% soil, 10% phosphogypsum + 3% bentonite + 87% soil and 10% phosphogypsum + 6% bentonite + 84% soil. X-ray diffraction and scanning electron microscopy were used to analyze the mineralogy, while the hydromechanical performance was evaluated through compaction, hydraulic conductivity, and unconfined compressive tests. Modified free swell tests and modified Atterberg limits were used to test compatibility with NaCl, NaOH and ethanol. A solubilization test was carried out to investigate the presence of inorganic contaminants in the phosphogypsum. The addition of phosphogypsum increased the optimum water content in the compaction curves, did not change the hydraulic conductivity and decreased the unconfined compressive strength of the mixtures. The addition of bentonite increased the optimum water content, reduced the hydraulic conductivity, and increased the unconfined compressive strength. The possibility of dissolution of gypsite (main component of phosphogypsum), the problems that may arise from the interaction with chemical products, and the risk of manganese release in the subsoil lead to the conclusion that phosphogypsum is not suitable to be used in liners. However, soil-bentonite-phosphogypsum mixtures were considered eligible materials to be used in impermeable layers of other geotechnical works.
每年,全世界生产数百万吨磷石膏,这是化肥工业的副产品。由于其中只有一小部分被重复使用,本研究分析了在岩土工程中重复使用这种材料的一种新选择,即与红土和膨润土混合,用于建造卫生填埋场的衬垫。试验四种成分:100%土、10%磷石膏+ 90%土、10%磷石膏+ 3%膨润土+ 87%土和10%磷石膏+ 6%膨润土+ 84%土。利用x射线衍射和扫描电镜对其进行了矿物学分析,并通过压实、导水性和无侧限压缩试验对其流体力学性能进行了评价。采用改进的自由膨胀试验和改进的Atterberg极限来测试与NaCl、NaOH和乙醇的相容性。对磷石膏中无机污染物的存在进行了增溶试验。磷石膏的加入增加了压实曲线上的最佳含水量,但没有改变混合料的水力导率,降低了混合料的无侧限抗压强度。膨润土的加入提高了最佳含水量,降低了导流系数,提高了无侧限抗压强度。石膏(磷石膏的主要成分)溶解的可能性,与化学产品相互作用可能产生的问题,以及在底土中释放锰的风险,导致磷石膏不适合用于班轮。然而,土壤-膨润土-磷石膏混合物被认为是用于其他岩土工程的防渗层的合格材料。
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引用次数: 0
Integrated use of georadar, electrical resistivity, and SPT for site characterization and water content estimative 综合使用地质雷达、电阻率和SPT进行现场表征和含水量估算
IF 0.5 Pub Date : 2023-06-19 DOI: 10.28927/sr.2023.006422
Érdeson Farias, S. Machado, H. Giacheti, A. Cerqueira
Geophysical methods are potent tools for geotechnical site characterization in a nondestructive way. They improve the extrapolation of punctual data from direct survey methods, allowing a fast and cost-effective evaluation of large areas. Ground Penetrating Radar (GPR) and DC electrical resistivity (ER) are the most requested methods for geotechnical and geoenvironmental applications. Their use, however, is usually uncoupled, with no sharing of information from one method to another to improve data interpretation. This case study illustrates the development of protocols and scripts in R© programming language for ER and GPR data analysis with Standard Penetration Tests (SPT) data to produce more accurate information on subsurface conditions concerning lithology, water content, and groundwater table (GWT) position. The SPT data were used to associate resistivity ranges with different soil lithologies and GPR pulse velocities for estimating the soil water content. Estimated water content values aided in interpreting ER data and locating the groundwater table. The contacts between layers in the radargrams allowed the refinement of the ER model, rendering 3D volumes for each soil layer in situ.
地球物理方法是以无损方式进行岩土工程现场表征的有力工具。它们改进了直接调查方法对准时数据的推断,从而能够对大面积进行快速且具有成本效益的评估。探地雷达(GPR)和直流电阻率(ER)是岩土工程和地质环境应用中最需要的方法。然而,它们的使用通常是不耦合的,没有从一种方法到另一种方法共享信息来改进数据解释。本案例研究说明了用R©编程语言开发的协议和脚本,用于ER和GPR数据分析以及标准贯入试验(SPT)数据,以产生有关岩性、含水量和地下水位(GWT)位置的地下条件的更准确信息。SPT数据用于将电阻率范围与不同的土壤岩性和GPR脉冲速度相关联,以估计土壤含水量。估计的含水量值有助于解释ER数据和定位地下水位。雷达图中各层之间的接触允许对ER模型进行细化,从而在现场绘制每个土层的3D体积。
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引用次数: 0
Lateritic soil deformability regarding the variation of compaction energy in the construction of pavement subgrade 路面路基施工中压实能变化对红土变形能力的影响
IF 0.5 Pub Date : 2023-06-05 DOI: 10.28927/sr.2023.009922
Paula Pascoal, Amanda Sagrilo, M. Baroni, L. Specht, D. Pereira
The performance of the subgrade towards the main deterioration mechanisms must be considered in the pavement structure design. Thus, this paper discusses the resilient modulus and permanent deformation evaluation of a pedological horizon of a Brazilian lateritic soil deposit, comparing samples compacted in the laboratory at the three compaction energies (standard, intermediate and modified) and undisturbed samples. Physical, chemical, and mechanical characterization tests were conducted. The cyclic tests were performed in repeated load triaxial tests and according to the current Brazilian standards. Five mathematical models widely used were employed to verify the resilient modulus behavior of the sample conditions, in which the Compound and Universal models showed the best correlations. For permanent deformation, the model was used, which well-expressed the plastic behavior of the analyzed conditions. Although all cases appeared to attend the shakedown criteria, some samples did not reach the deformation rate required by the standard. As the compaction energy was increased, the resilient modulus increased, and the permanent deformation decreased. Therefore, there is a substantial modification of the material behavior by increasing the compaction.
在路面结构设计中,必须考虑路基对主要劣化机制的性能。因此,本文讨论了巴西红土矿床土层的弹性模量和永久变形评估,比较了在实验室中以三种压实能量(标准、中间和改良)压实的样品和未扰动样品。进行了物理、化学和机械特性测试。循环试验是根据巴西现行标准在重复荷载三轴试验中进行的。采用了五个广泛使用的数学模型来验证样品条件的弹性模量行为,其中复合模型和通用模型显示出最好的相关性。对于永久变形,使用了该模型,该模型很好地表达了所分析条件的塑性行为。尽管所有情况似乎都符合安定性标准,但一些样品没有达到标准要求的变形率。随着压实能量的增加,弹性模量增加,永久变形减小。因此,通过增加压实度,对材料性能进行了实质性的改变。
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引用次数: 1
Geotechnical behavior of gravity dams built on sedimentary rocks: pore pressures and deformations analysis of Dona Francisca HPP foundation 沉积岩上重力坝的岩土工程特性:多纳方济各水电站地基的孔隙压力和变形分析
IF 0.5 Pub Date : 2023-06-01 DOI: 10.28927/sr.2023.013622
Verlei Santos, L. Bressani, Camila Smirdele
In Brazil, some dams have been built on sedimentary rock masses, which usually present greater deformability and permeability in comparison to metamorphic or igneous rock masses. This article describes a case study whose goal is to present and analyze the main data related to the monitoring of foundation behavior of the Dona Francisca dam, whose foundation is essentially constituted by sedimentary rocks. Dona Francisca gravity dam is a hydroelectric power plant (HPP) and was built in 2000, on the Jacuí River, in the central region of the Rio Grande do Sul State, Brazil. The analysis of the foundation behavior was done in terms of pore pressures and deformations recorded during seventeen years of dam operation. The geological and geotechnical conditions of the foundation are related to the Formação Caturrita rocks, made up mainly of sandstones and intercalated levels of siltstone and argillite. In the first five years of operation there was an intense stabilization process of the foundation rocky mass. After this period, it was verified the occurrence of stabilization at a lower rate. The deformation of the Dona Francisca HPP foundation is higher when compared with other larger dams, such as the Itaipu HPP dam. It was carried out an analysis of the 18 vibrating wire piezometers data, allowing a global assessment about the uplift water pressures behavior. Most piezometers indicated a reduction in the pore pressure values over time with a current trend of stabilization, and readings below the control values recommended in design.
在巴西,一些大坝建在沉积岩体上,与变质岩或火成岩体相比,沉积岩体通常具有更大的变形性和渗透性。本文描述了一个案例研究,其目的是提供和分析与Dona Francisca大坝地基性能监测相关的主要数据,该大坝的地基基本上由沉积岩组成。Dona Francisca重力坝是一座水电站,建于2000年,位于巴西南里奥州中部的Jacuí河上。根据大坝运行17年期间记录的孔隙压力和变形,对地基性能进行了分析。基础的地质和岩土条件与Formação Caturrita岩石有关,该岩石主要由砂岩组成,夹有粉砂岩和泥质岩。在运营的前五年,地基岩体经历了一个强烈的稳定过程。在此期间之后,证实了稳定的发生率较低。与其他较大的大坝(如Itaipu水电站大坝)相比,Dona Francisca水电站基础的变形更高。它对18个振弦测压计的数据进行了分析,从而对扬压力的行为进行了全面评估。大多数测压计显示,随着时间的推移,孔隙压力值会随着当前的稳定趋势而降低,读数低于设计中建议的控制值。
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引用次数: 0
The 2022 Pacheco Silva lecture: The influence of residual loads on pile foundation behavior 2022年Pacheco Silva讲座:剩余荷载对桩基行为的影响
IF 0.5 Pub Date : 2023-05-24 DOI: 10.28927/sr.2023.002523
B. Danziger
Residual loads can affect the load transfer and the settlement-induced in-service loadings, although they do not alter the bearing capacity. When residual loads are present and not measured or evaluated, the settlement estimate is greater than predicted if these loads are known. Residual loads can be measured when the pile instrumentation is nullified before pile installation, in the case of displacement piles, or before the first loading in non-displacement piles, such as bored cast-in-place piles, continuous flight auger piles, and micro-piles. In the case of underpinning foundation and piled raft, when the loading transfer is shared by the original and new foundation, or by the piles and the raft, it is essential to know the stiffness of each foundation element to estimate the load partition. If residual loads are present, pile stiffness is greater than when not considered in the design. The paper revisits this theme of practical relevance. A historical review of the most relevant research involving pile residual load measurements, pile loading tests including the interpretation of residual loads locked at a pile toe, and a new procedure for residual loads prediction are provided. A comparison is made of the experimental residual loads observed in some of the instrumented cases and the values estimated with the suggested procedure. The development of residual loads at the pile toe as a function of the toe resistance to total capacity ratio is very similar to the variation of the soil density as a function of soil moisture content in soil compaction.
残余荷载会影响荷载传递和沉降引起的在役荷载,但不会改变承载力。当残余荷载存在且未测量或评估时,如果已知这些荷载,则沉降估计大于预测。在安装桩前、位移桩、钻孔灌注桩、连续飞螺桩、微孔桩等非位移桩的首次加载前,均可测量残余荷载。在托存基础和桩筏的情况下,当原基础和新基础分担荷载传递时,或者桩和筏分担荷载传递时,了解每个基础单元的刚度是估算荷载分配的必要条件。如果存在残余荷载,则桩的刚度大于设计中未考虑的情况。本文回顾了这一具有实际意义的主题。本文回顾了相关研究的历史,包括桩剩余荷载测量、桩荷载试验(包括解释锁定在桩趾处的剩余荷载)以及剩余荷载预测的新方法。在一些仪器情况下观察到的实验残余载荷与用建议的方法估计的值进行了比较。桩端残余荷载随桩端阻力与总容量比的变化规律与土密度随土壤含水量的变化规律非常相似。
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引用次数: 0
Semi-empirical method for the bearing capacity of continuous flight auger piles based on installation energy 基于安装能量的螺旋钻孔灌注桩承载力的半经验方法
IF 0.5 Pub Date : 2023-05-24 DOI: 10.28927/sr.2023.012522
C. Silva, José Camapum de Carvalho
The prediction of load capacity and the control of the execution of the Continuous Flight Auger (CFA) piles are often exercised with components of empiricism and intuition. This fact is often added to the uncertainties arising from the formation of the soils and the limitations of preliminary studies that support the project design. In this context, aiming to aid the executive control of CFA, a semi-empirical method is proposed based on the soil type, geometric dimensions of the piles, and the installation energy obtained during the pile excavation. The method makes it possible to determine the CFA pile load capacity during the execution process of each pile of pilling. As a consequence of the proposed method, the settlement of each pile can be controlled through the quantification of the energy required or the work carried out to excavate each pile through a specific software installed in the machinery monitoring system that increases the safety and reliability of the piling.
连续飞行螺旋钻孔(CFA)桩的承载能力预测和施工控制通常采用经验主义和直觉的成分。这一事实往往增加了土壤形成产生的不确定性,以及支持项目设计的初步研究的局限性。在此背景下,为了帮助CFA的执行控制,基于土壤类型、桩的几何尺寸和桩开挖过程中获得的安装能量,提出了一种半经验方法。该方法可以在每根桩的打桩过程中确定CFA桩的承载能力。由于所提出的方法,每个桩的沉降可以通过量化所需的能量或通过安装在机械监控系统中的特定软件进行挖掘来控制,从而提高桩的安全性和可靠性。
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引用次数: 0
Use of longitudinal wave in non-destructive methods: approach to foundation and retaining elements 纵波在无损检测方法中的应用:地基和挡土墙构件的探讨
IF 0.5 Pub Date : 2023-05-23 DOI: 10.28927/sr.2023.013222
Isabela Silva, V. Faro
Non-destructive tests (NDT) are used to verify the length or integrity of elements embedded in soils or rocks. These elements can be piles in foundations or nails and tiebacks in retaining walls. NDTs differ by the types of waves, ways to generate and receive the signal and to analyze data. Tests using sonic wave do not require a pre-installed pipe or wire and they are based on acoustic impedance theory. Despite its dissemination on piles, the application in retaining elements is recent and requires more studies to increase knowledge about these methods. This paper aims to present studies of sonic wave methods in foundation and retaining elements, presenting results, similarities, and differences. Studies from different dates are presented with their relevance, considerations for the different types of elements tested, objectives and methodologies used, to evidence the variables involved within this solution. The sonic test in foundation is widespread and has a greater number of studies. Withing this paper, the variables that interfere in the results of these methods were observed: the velocity of propagation of the sonic wave, the soil stiffness, the location of wave generation and reception and the type of hammer used, evidencing the necessity of further studies, especially in retaining elements.
无损检测(NDT)用于验证嵌入土壤或岩石中的构件的长度或完整性。这些元素可以是地基上的桩或挡土墙上的钉子和回箍。ndt的不同之处在于波的类型、产生和接收信号的方式以及分析数据的方式。使用声波的测试不需要预先安装管道或电线,它们基于声阻抗理论。尽管它在桩上传播,但在挡土单元中的应用是最近的,需要更多的研究来增加对这些方法的认识。本文旨在介绍声波法在地基和支护构件中的研究,并给出结果、异同。介绍了不同时期的研究及其相关性、对测试的不同类型要素的考虑、所使用的目标和方法,以证明该解决方案中涉及的变量。地基声速试验应用广泛,研究较多。在本文中,观察了干扰这些方法结果的变量:声波的传播速度,土壤刚度,波的产生和接收位置以及所使用的锤的类型,证明了进一步研究的必要性,特别是在保留元素方面。
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引用次数: 0
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Soils and Rocks
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