Dilatometric Tests Research Articles

Deeper Vs profile constraining the dispersion curve with the ellipticity curve: A case study in Lower Tagus Valley, Portugal

Shear wave velocity profile and bedrock depth are key parameters for seismic site response estimation and a reliable tool to evaluate liquefaction potential in soil deposits. They can be determined using in-situ geotechnical tests such as the seismic Cross-Hole (CH), seismic Cone Penetration Test (SCPT), seismic Dilatometer Test (SDMT), or through geophysical surface wave methods. The main advantages of surface wave methods are their non-invasive nature and the ability to characterize the shear wave velocity of the soil at a larger scale. However, the investigation depth in general is less than 20 m. Using the Rayleigh ellipticity curve to constrain the dispersion curve from active and/or passive measurements, deeper Vs-profile is obtained.In this study, the Vs profile of the soil at a site located over Lower Tagus alluvial Valley was obtained using different surface wave methods. For this purpose, ambient vibration measurements using a single three-component seismic station were made, to complement active and passive linear measurements. The Rayleigh wave ellipticity curve was computed from the single station recordings using the RayDec method and dispersion curves were estimated with the array recordings processed using f-k based methods: MASW, ReMi and conventional f-k method for non-linear array data. A joint inversion procedure was applied to the data and the results were compared with Vs profiles obtained from direct measurements with Cross-Hole and SDMT tests. The results show that considering the passive ellipticity curve in the joint inversion process with the dispersion curve, it is possible to obtain deeper and less scattered Vs profiles.

Research of thermodynamic properties of mid-infrared single crystal ZnGeP2

Chalcopyrite ZnGeP2 single crystal with sufficient size and quality was grown by modified vertical Bridgman method. The thermal expansion coefficients along a-axis and c-axis, αa and αc, were evaluated from the results of thermal dilatometer tests carried out in the range of 300–600K. It is found that both αa and αc achieve positive values and αa is always larger than αc in the whole range indicating that the thermal expansion of the crystal exhibits anisotropic behavior. We selected the sample of c-axis and measured its thermal conductivity and molar specific heat. On this basis, the Grüneisen parameters of c-axis at different temperatures were calculated. Using these Grüneisen parameters, the lattice thermal conductivities have been deduced by one correction formula and we found that they are very close to the experimental results.

Determination of the presence of microstructure in a soil using a seismic dilatometer

This article shows an approach for investigating the presence of microstructure in a soil based on the results obtained by seismic dilatometer (SDMT). Three main parameters are considered: intermediate dilatometer test (DMT) parameters material index (ID) and horizontal stress index (KD) and small strain stiffness (G0) obtained by shear wave velocity (Vs) measurements. The approach is engineering-oriented since it is simple, fast, inexpensive, and based directly on in situ measurements. We found that with increasing microstructure (cementation and aging) the ratio of measured to estimated G0 increases, which could be used to improve interpretation of empirically determined geotechnical parameters from DMT results. Applications of a DMT-based, CPT-based and Vs-based correlations for determination of effective peak friction angle of sands, with and without presence of microstructure, are evaluated. Finally, we propose an approach to reducing the influence of microstructure on K0–KD correlation in a clay.

Design, Use, and Interpretation of an Instrumented Flat Dilatometer Test

Abstract The flat dilatometer test (DMT) has been increasingly used as a routine geotechnical site characterization tool in numerous parts of the world for over 30 years. In the meantime, with the rapidly growing metal 3D printing technique, engineers now can design robust, durable devices that are impossible to make by traditional means. This paper presents the development of an instrumented dilatometer (idilatometer) that has continuous measurements of a piston expansion up to 2.35 mm and pore pressure at the piston center with the assistance of a metal 3D printing technique. A field-testing program consisting of an instrumented flat dilatometer test (iDMT), a DMT, and a cone penetration test (CPT) positioned 1 m apart from each other was carried out in a site in Belgium composed of soil that ranged from silty sands to sandy silts. Interpretation techniques are provided to evaluate the test results, such as the conceptual contact pressure pc based on the full pressure-displacement curve in the iDMT as an alternative for p0 in the DMT. The pressure required for a 0.56-mm piston expansion is found to be equivalent to that of a 1.1-mm central membrane displacement, based on a finite element method (FEM) simulation approach with the assumption of linear elastic soils and a modified displacement boundary. A comparison made between test results from the iDMT, the DMT, and the CPT shows reasonable trends and suggests the use of the iDMT in future soil investigation.

Influence of titanium on transformation behaviour during continuous cooling of boron microalloyed steels

ABSTRACTContinuous cooling transformation (CCT) characteristics and prior-austenite grains of boron microalloyed steels with and without titanium were investigated to obtain the necessary information for heat treatment of these steels. Transformation characteristics were determined by using dilatometer tests, microscopic observation, and hardness measurements. In addition, the effects of titanium addition on the sizes of prior-austenite grains and precipitates were analysed. The results show that the changes in austenite grain size are not very distinct, and adding titanium only slightly refines the austenite grains. The CCT diagrams showed that the ranges of transformation products were shifted to the right side by the addition of titanium. The ferrite transformation starting temperatures were reduced on addition of titanium. Titanium addition induced decreased critical cooling rates for bainite transformations. The hardenability of boron microallyed steel is increased by adding titanium because more boron segregate to prior-austenite grain boundaries.

Korelativni odnosi za definisanje deformabilnosti stene

In the framework of geotechnical investigations of the rock mass at the partition site MHE Bočac 2 (BiH), Jelašnica dams on the same river in southern Serbia and nine partition sites of hydroelectric power plants on the river Ibar, detailed geotechnical investigations of the rock mass were carried out. They included exploration drilling with the definition of quasihomogenic zones within the drilled core, determination of RQD for each separated quasi-chemical zone, dilatometric tests in each well, seismic ventilation between exploratory wells or seismic carotid, core testing by the Point Load method and laboratory tests of the single-axial strength of the samples. By connecting the results of the one-axial strength, the velocity of the elastic waves and the quality of the rockl mass (RMR), i.e. these indirect data for defining the deformability of the rock masses with the obtained results of in situation deformability testing, with the results of dilatometric tests, the analysis of correlation bonds is carried out which is applied in engineering geological or geotechnical practice. As is known, in engineering practice, the following correlations are used to define the deformation module: D = f(RMR); D= f(RMR,σci); D= f(Vp) i D = f(Vp, σci). After the analysis, a correlation was applied which included all three indirect data and it gave the closest data for defining the deformability of the rock mass.

Построение диаграмм распада переохлажденного аустенита в стали на основе численного анализа результатов дилатометрических испытаний

Построение диаграмм распада переохлажденного аустенита в стали на основе численного анализа результатов дилатометрических испытаний

Rammed aggregate pier installation effect on soil properties

This paper describes the changes in in situ index properties following installation of rammed aggregate piers in a loose sand deposit in New Madrid, Missouri, with a particular focus on the time-dependent strength gain, commonly called sand ageing, as indicated by increased cone penetration test (CPT) tip resistance and dilatometer test (DMT) indices. The method of disturbing the soil and the magnitude of disturbance significantly influence the magnitude of sand-ageing effects. This paper provides the first data on sand ageing following the installation of displacement rammed aggregate piers. In this study, CPT and DMT were performed both immediately before and after the installation of piers. Additionally, CPTs were performed 1 month following the installation of piers. The DMT horizontal stress index increased roughly 100% and the dilatometer modulus increased ∼200% in a loose clean sand layer immediately following the installation of the piers. The CPT tip resistance increased roughly 100% in this layer immediately following the pier installation and a further 33% in the month following the installation.

Stability Analysis and Support System Design of Penstock Tunnels Bifurcation with Headrace Tunnel of Rudbare-Lorestan Dam Project

Summary In this research, stability of penstock tunnels bifurcation with headrace tunnel of Rudbare-Lorestan dam powerhouse was studied. Due to the weak rock masses at the bifurcation area, the numerical modeling using FLAC3D was performed. According to the results of numerical modeling and determination of plastic zone and the empirical methods, the temporary support system consists of shotcrete and rock bolt with adequate length are suggested. Based on laboratory and in situ tests, the geomechanical parameters are determined. Introduction Today, large underground structures are constructed in order to transfer the water, oil and gas storage, underground power plants, radioactive waste repositories and etc. With the development and upgrade of infrastructures, tunnel construction is increasing all over the world and tunnel engineers are more aware of the importance of the safety and economics of tunnel construction. Stability of underground structures depend on size and geometry of construction, excavation technique, in situ stress conditions and support system and its installation time. Methodology and Approaches In order to estimate the deformation modulus of the rack mass in the headrace tunnel, in situ tests including of plate loading and dilatometer tests were performed. Then elasto-plastic behavior was defined for the rock mass by mohr-columb criterion and model was executed numerically to reach static stability. The Bifurcation cavern have been excavated by heading and benching method that is executed through drill and blasting technique. Results and Conclusions The empirical method suggest shotcrete with rock bolts to support weak rock masses. Also the numerical analysis demonstrate the installation of rock bolts with shotcrete as a temporary support system. Due to the large plastic zone caused by excavation processes, the value of the advancing step 0.8 m was determined. Also, the analysis of rock mass plastic zone in bifurcation area determined a suitable length of 6 meters for rock bolts. During the excavating of rock pillars, the value of change in the axial force acting on the rock bolt in the right wall of the tunnel No. 1, was increased. Also, the excavation of tunnel No. 2 at a distance of 11 meters from the tunnels No. 1, No. 4 and No. 5, was shown the less influence on the value of axial forces applied to the rock bolts. After the 16 stages of excavation advancement steps and installation of support systems, the maximum values of displacement in the roof, floor and walls of the bifurcation, were respectively 2.8, 3.67 and 1.5 cm

Uncovering the local inelastic interactions during manufacture of ductile cast iron: How the substructure of the graphite particles can induce residual stress concentrations in the matrix

Recent X-ray diffraction (XRD) measurements have revealed that plastic deformation and a residual elastic strain field can be present around the graphite particles in ductile cast iron after manufacturing, probably due to some local mismatch in thermal contraction. However, as only one component of the elastic strain tensor could be obtained from the XRD data, the shape and magnitude of the associated residual stress field have remained unknown. To compensate for this and to provide theoretical insight into this unexplored topic, a combined experimental-numerical approach is presented in this paper. First, a material equivalent to the ductile cast iron matrix is manufactured and subjected to dilatometric and high-temperature tensile tests. Subsequently, a two-scale hierarchical top-down model is devised, calibrated on the basis of the collected data and used to simulate the interaction between the graphite particles and the matrix during manufacturing of the industrial part considered in the XRD study. The model indicates that, besides the viscoplastic deformation of the matrix, the effect of the inelastic deformation of the graphite has to be considered to explain the magnitude of the XRD strain. Moreover, the model shows that the large elastic strain perturbations recorded with XRD close to the graphite–matrix interface are not artifacts due to e.g. sharp gradients in chemical composition, but correspond to residual stress concentrations induced by the conical sectors forming the internal structure of the graphite particles. In contrast to common belief, these results thus suggest that ductile cast iron parts cannot be considered, in general, as stress-free at the microstructural scale.

Effect of Heat Treatments and SiC Content in the Mechanical Properties and Microstructure of Self-Lubricating Steels

The objective of the present work was to study the effect of heat treatments in the microstructure, graphite nodules and mechanical properties of self-lubricating steels, to achieve this, self-lubricating steels (Fe + 0.45C + 4Ni + 1Mo %wt) and additions of 2 and 3 %wt SiC were fabricated. They were consequently heat treated in 3 different conditions: martempering at 180 °C and tempering at 530 °C and 300 °C respectively and austempering at 300 °C. Hardness, yield strength, tensile strength and work hardening behavior were studied in as-sintered and heat-treated samples. The microstructure was analyzed by optical microscopy, scanning electron microscopy, Raman spectroscopy and micro-hardness. The transformation temperatures were determined using dilatometric tests. Results show that the presence of dissolved Si in the matrix due to SiC dissociation notably affects the morphology of the microstructure and transformation temperatures also affecting post heat treatment mechanical properties. The structure of graphite nodules produced by SiC dissociation is nott significantly affected by the heat treatments.

Soil Overconsolidation Changes Caused by Dynamic Replacement

In the dynamic replacement method (DR) the soil is improved by initially dropping a large weight (typically 8-20 t) pounder from a significant height up to 25 m. The created crater is filled with a stronger material (gravel, rubble, stone aggregate, debris), and the pounder is dropped once or multiple times again. The construction of dynamic replacement pillars influences the parameters of the adjacent soil. It results from the energy generated by dropping a pounder into the soil. In the current practice, these changes are not taken into the account during the design. This paper focuses on the changes of overconsolidation ratio (OCR) and in situ coefficient of lateral earth pressure (K) values estimated base on cone penetration test (CPTU) and Dilatometric test (DMT) performed at a test site. A single column was constructed and the ground around the column was examined using CPTU and DMT, performed at different distances from the column centre (2, 3, 4 and 6 m) and at different time intervals (during construction and 1, 8, 30 days later). The column was constructed in so-called transition soils (between cohesive and non-cohesive). While interpreting the results of the research, the authors addressed the matter of choosing the procedure of OCR and K indication for transition soils (in this case described as silts and/or sandy silts). Overconsolidation changes may differ depending on the chosen analysis procedure (for cohesive or non-cohesive soils). On the basis of the analysis presented in the paper and the observation of soil (acknowledged as cohesive according to macroscopic observations) during column excavation, it was decided that for more detailed analyses methods dedicated to cohesive soils should be applied. Generally, it can be stated that although the changes were complex, DR pillar formation process resulted in the increase of these parameters. The average increases of OCR and K values were 25% and 10% respectively. The post installation values are not significant from the engineering point of view, but they represent the influence of the formation process of only a single column. The described results indicate that Priebe’s column dimensioning method should be applied with caution, as it assumes the value K=1 which was not obtained in the described research. The results from the conducted tests indicate that different mechanisms occur during stone column formation with vibro-replacement and dynamic replacement. As the authors did not manage to find literature describing the results of K tests in the surrounding of a DR column, the presented results should be acknowledged as significant for designers who will apply the dynamic replacement method.

Tempering stability of Fe–Cr–Mo–W–V hot forging die steels

The tempering stability of three Fe–Cr–Mo–W–V hot forging die steels (DM, H21, and H13) was investigated through hardness measurements and transmission electron microscopy (TEM) observations. Both dilatometer tests and TEM observations revealed that DM steel has a higher tempering stability than H21 and H13 steels because of its substantial amount of M2C (M represents metallic element) carbide precipitations. The activation energies of the M2C carbide precipitation processes in DM, H21, and H13 steels are 236.4, 212.0, and 228.9 kJ/mol, respectively. Furthermore, the results indicated that vanadium atoms both increase the activation energy and affect the evolution of M2C carbides, resulting in gradual dissolution rather than over-aging during tempering.

A Correlation Study Between Mechanical Properties and Morphological Variation of 20MnMoNi55 Steel

Mechanical properties of nuclear reactor pressure vessel materials need to be assessed for degradation while operating under an irradiated condition, but conventional destructive tensile testing is not possible in such cases. In the present paper, a methodology is suggested which relates microstructural parameters to macro-mechanical properties of 20MnMoNi55 steel. Morphological variation of 20MnMoNi55 steel has been achieved through inter-critical heat treatment based on the phase fraction of constituent phases. The inter-critical temperature range of as-received material is determined through dilatometric testing. A color etching technique has been adopted for identification of different phases present in as-received and heat treated steel specimens. Vickers hardness values of each constituent phase as obtained from micro-hardness testing is correlated and standardized with the specified color code of each phase through image analysis of colored optical micrographs. Finally macro-hardness, obtained from the standard mixture rule based on micro-hardness and volume fraction of constituent phases, is correlated with tensile properties.

Comparison between deformation modulus of rock mass measured by plate jacking and dilatometer tests

For determination of the in-situ deformation modulus of rock mass at Bakhtiari Dam site, located in south-west of Iran, plate jacking tests (PJT) and dilatometer tests (DLT) carried out during the geotechnical investigations. In this study, the results of PJTs and DLTs were compared. This comparison involves 89 vertical and horizontal PJTs and 83 DLTs carried out in 6 rock units of Sarvak formation. Although, both PJTs and DLTs in the Bakhtiari Dam site were performed in same geological and geotechnical conditions, but there are not sufficient side by side data to make a paired two samples correlation. Therefore, the mean of in-situ data was compared at each rock unit. Besides Mann–Whitney U tests were performed to compare in-situ test results. The comparison shows that the deformation modulus measured by both methods has no significant differences. However, in low quality rock masses the moduli measured by the use of DLTs were greater than the modulus measured by PJTs. Conversely, in high quality rock masses the results of PJTs were greater than DLT’s.

The overconsolidation ratio of eemian gyttja determination

Abstract The overconsolidation ratio of eemian gyttja determination. The overconsolidation ratio is an important parameter that determines the value of stress history exerted in the past on the subsoil in the geotechnical engineering. Overconsolidation ratio (OCR) is one of the main criteria conditioning soil behavior and characteristics. To know the relation between geological background, history and mechanical behavior of the soil, aims a knowledge that can help engineers who often have to predict soil behavior based upon the soil geological history and a geotechnical data. In order to evaluate the overconsolidation ratio of eemian gyttja, it is necessary to restore this soft soil as much as possible to the in situ conditions. The eemian gyttja is an organic soft soil from the “Zoliborz channel” located in Warsaw. These soils are used as a base construction in the foundation engineering. In practical geotechnical engineering, evaluation of stress history is based on the overconsolidation ratio. The overconsolidation ratio is one of the basic parameters for the geotechnical design of the structure. Determination of this parameter using for example dilatometer tests, is usually based on empirical formulas which were established in different countries. Therefore, regional geotechnical conditions could have substantially affected on the empirical relationships. The laboratory tests are used to determinate the preconsolidation pressure and then the overconsolidation ratio. The laboratory tests were made in the automatic oedometer and the in situ tests were carried out on the dilatometer test (DMT). The paper presents results of determination the overconsolidation ratio of eemian gyttja from the laboratory and in situ tests. The studies have shown that the values of the overconsolidation ratio determination from the laboratory tests are a little higher than determination from the in situ tests.

Hot Stamping of Boron Steel Using Partition Heating for Tailored Properties: Experimental Trials and Numerical Analysis

Hot-stamped components with tailored properties are becoming popular for their better performance in collision. In this article, an M-shaped part with varying properties was formed by hot stamping using partition heating. Different soaking temperatures induce different austenite fractions at the different regions of the blank, resulting in the partitioned microstructure and mechanical properties in a single part. In the high-temperature region, the average tensile strength and elongation are 1565 MPa and 8.65 pct, respectively, and the average tensile strength and elongation are 626 MPa and 24.37 pct, respectively, in the low-temperature region. A finite element model of hot stamping using partition heating was established based on the relationship of austenite fraction with heating temperature determined by the dilatometer test and the stress–strain curve of 22MnB5 with different austenite fractions acquired from the hot tensile test.The differences of temperature, thickness, and Vickers hardness in different zones of the M-shaped part during forming and quenching stages were analyzed. The effects of hot stamping parameters, such as stamping velocity and heating temperature, on the forming and mechanical properties of the tailored M-shaped part were investigated, providing theoretical guidance for the production of tailored hot-stamped components using partition heating.

Landslides Detection by Released Zone Depth Determination in North-West Wall of Anguran Mine Using Flat Dilatometer Test

Anguran Lead and Zinc Mine is the largest lead and zinc mine in Iran and the Middle East. In 2006, the north-west wall of this mine had an enormous collapse (approximately 30 million tons). Concerns about another collapse of this wall is more than before with the increasing depth of the ore deposit nowadays. Therefore, the mine development program for excavation the whole of ore deposit, needs to ensure stabilization of the NW wall. In the current research, to estimate weathered depth and probable collapses of the NW wall, the flat dilatometer in situ test (DMT) was used. The flat dilatometer test had the lowest distortions caused by the penetration in the surroundings formations, due to its ground insertion methods without needing borehole drilling. Using this test, it was possible to identify relaxation zones and collapsible zones. Depth of weathered zone was determined 0.5–2 m in the foot of bench and the whole of this weathered zone was distressed by the DMT analyzed data. The whole of landslides were identify surface active and didn’t identify quiescent slip surface in this zone.

The first Italian blast-induced liquefaction test (Mirabello, Emilia-Romagna, Italy): description of the experiment and preliminary results

Soil liquefaction can result in significant settlement and reduction of load-bearing capacity. Moreover, the increase and the accumulation of pore pressure during an earthquake and its post-seismic dissipation can generate permanent deformations and settlements. The quantitative evaluation of post-liquefaction settlements is of extreme importance for engineering purposes, i.e. for earthquake-resistant design of new buildings and safety evaluation of existing ones. Quantifying the extent of these phenomena is, however, rather difficult. Uncertainties arise from the stochastic nature of the earthquake loading, from the simplifications of soil models, and from the difficulty in establishing correlations between the pre-earthquake soil state and the post-seismic deformations. Field scale liquefaction tests, under controlled conditions, are therefore important for a correct quantification of these phenomena. Recent experiences (e.g. New Zealand, United States) show that liquefaction can be induced and monitored with field scale blast tests to study the related effects on soil geotechnical properties. Within this framework this paper introduces the preliminary results obtained from a research project on blast-induced liquefaction at the field scale; tests were performed at a trial site located in Mirabello (Ferrara, Italy), a village strongly affected by liquefaction phenomena during the 2012 Emilia Romagna earthquake. Invasive tests, such as piezocone, seismic dilatometer and down-hole tests, and non-invasive tests were carried out before and after the execution of two blast test sequences to study the variation in physical properties of the soils. Pore pressure transducers, settlement profilometers, accelerometers and an instrumented micropile were installed with the objective of measuring, during and after the detonations, the generation and subsequent dissipation of the pore pressure, the vertical deformations, and the blast-induced ground motions respectively. Variations in load distribution on deep foundations due to soil liquefaction were also evaluated on a test micropile instrumented with a strain gauge chain. Topographical surveys were carried out to measure ground surface settlements. Laboratory tests and trenches also provided increase understanding of the site characteristics.

Geo-engineering properties of Eemian peats from Radzymin (central Poland) in the light of static cone penetration and dilatometer tests

The paper presents the results of field studies testing the reaction of Eemian peats on the mechanical effect of standard measurement tools (CPT/CPTU, Marchetti dilatometer). Based on the collected undisturbed samples, macroscopic observations were made and SEM observations were conducted to identify the microstructural features. A fibrous structure and advanced diagenetic changes have been noted in the studied peats despite their relatively young age. These may have resulted from an exceedingly strong structural reinforcement, which causes that the studied sediments cannot be treated as low-bearing soils. Diagenetic processes caused farfetched changes of the mechanical properties, which is reflected e.g. in classification normograms. Standardized diagrams may lead to false conclusions. The presented studies of organic soils are an example of strong influence of structural features and diagenetic phenomena on the results obtained for native soils. At the same time, they imply particular caution in the interpretation of the substratum properties based only on the commonly used in situ tests. The values and variability of the collected parameters have been presented as frequency distributions. Additionally, the apparent character of the properties of preconsolidation parameters (OCR) has been shown.