Geotechnical Laboratory Tests Research Articles

Study of the major landslide at the community of Ropoto, Central Greece, mitigation and FBG early warning system design

This paper refers to the world known major landslide at the community of Ropoto, belonging to the Municipality of Trikala, in the Central part of Greece. The size of the landslide and the massive destruction of community’s infrastructure alarmed all the relevant public authorities, pushed by the community and the press, in order to find a fast and permanent solution to this longlasting geotechnical problem. Some of the community’s houses were partially affected, while others were totally destroyed and the time was ticking. The authors' intention was the complete determination of the geotechnical conditions of the entire community's area through a complete geotechnical field work, which wasn't conducted during the previous investigations (1976, 1979 and 1990). In addition, the proposition of immediate and long term remedial measures for the slope's stabilization, as well as the geostructure’s global behavior monitoring was of the author's highest priority. The geotechnical program included the drilling of four (4) 20 m deep sampling boreholes, along the axis of the landslide, in which piezometers and inclinometers were installed, the drilling of one (1) 111 m deep hydrogeological 0.25 m borehole, in order to immediately pump the excessive underground water. Based on the results from the geotechnical laboratory tests, a full scale landslide modeling, as well as a stability analysis of the slope was conducted, and remediation measures were calculated for immediate implementation. Finally, an advanced surveillance method using fiber optics (fiber Bragg grating) was further studied, in order to monitor the geostructure’s health, and to function as an early warning system.

Verification of the Ramberg-Osgood Material Model in Midas GTS NX with the Modeling of Torsional Simple Shear Tests

This study focuses on the back analysis of a geotechnical laboratory test with nonlinear finite element modeling using the Ramberg-Osgood material model. This model has been used by several authors recently for nonlinear ground response analysis and it has been implemented by Midas into their commercial finite element code Midas GTS NX 2014. The verification of the model for 1D nonlinear site response analysis can be found in the documentation of the software package. In this study, Torsional Simple Shear tests were modeled and a comprehensive study was performed to provide verification of the material model for static torsional loading and axisymmetric conditions.

Geotechnical Investigations and Estimation of Earthquakes Factors at an Industrial Qift City, Qena, Egypt

The present work dealt with the estimation of geotechnical parameters and earthquakes factors of poultry feed factory project constructing at an industrial Qift city, Qena, Egypt. The geotechnical parameters were including gradation parameters, shear velocity (Vs), shear parameters (frictional angle and cohesion), and allowable bearing capacity. The earthquakes factors were including soil coefficient (S), limits of constant value for elastic response spectrum (TB and TC), and specified value for begin of the constant displacement spectrum (TD). The present study was interested also in an estimation of design ground acceleration (ag). To achieve these objectives, five mechanical wash boreholes were conducted at ten meter depth. Fifty disturbed samples were collected. Geotechnical laboratory tests were carried out like grain size analyses, direct shear box, and shear velocity (Vs). Standard penetration test (SPT) as geotechnical field test was conducted. The results showed that the studied soils were classified as well graded and poorly graded sands (SP and SW) according to the unified soil classification system (USCS). The earthquakes factors including S, TB, TC, and TD were 1.80, 0.10, 0.30, and 1.20 respectively. The ag-value of the studied area was 0.10. According to Egyptian code for vibration and dynamic load foundations, the studied project area was classified as low potential seismic. According to Egyptian code for shallow foundation, the allowable bearing capacity of the studied sands ranging from 1.5 to 3 kg/cm2 at shallow foundation width must be not less than one meter. Shallow foundations like isolated footing or structural mat were recommended.

Determining lateral resistance of sleeper in railway ballast

Within a project of Technology Agency of the Czech Republic No. TA 04030889 “Operational diagnostic of qualitative indicators of railway tracks by means of gauging its spatial deformation.” Empirical cross-resistance tests of sleepers in railway ballast were carried out in geotechnical laboratory test field (GLTF) of the Transport research center in Brno (TRC). The tests were done in collaboration with Czech Technical University in Prague, Department of Railway Structures (ČVUT).

Variability of undrained shear strength cu within one organic soli layer

For the purpose of this article a program of geotechnical laboratory tests was performed on organic soil (mud) samples from one geological layer. All undisturbed samples were taken within the same excavation in square grid with a side about 30 cm. Differences between specimen parameters were found both at basic test results and at shear strength tests results. Based on all performed tests authors suggest carefulness in assuming geotechnical parameters of organic soil layers because of theirs spatial variability even in very close vicinity.

Manufacture of Bonded Granular Soil Using X-Ray CT Scanning and 3D Printing

This paper describes the use of X-ray tomography imaging of natural gravel specimens to create repeatable assemblages of bonded gravel-size resin specimens using a 3D printer. The paper describes how the resulting resin-based surrogate specimens have particle geometry and interparticle bonds that are a function of the original scanning image resolution and 3D printer resolution. Results of conventional triaxial compression testing of original source gravel specimens and constructed bonded specimens are compared. While there are quantitative differences in behavior between unbonded source and bonded duplicate specimens, the surrogate specimens are shown to have macroscale mechanical behavior that may be considered typical of some granular soils. The ability to generate identical surrogate bonded granular specimens with the same particle arrangement holds promise to remove the influence on geotechnical laboratory testing outcomes due to the unavoidable structural variation in specimens of natural granular assemblages.

Evaluation of liquefaction potential in an intermountain Quaternary lacustrine basin (Fucino basin, central Italy)

In this study, we analyse the susceptibility to liquefaction of the Pozzone site, which is located on the northern side of the Fucino lacustrine basin in central Italy. In 1915, this region was struck by a M 7.0 earthquake, which produced widespread coseismic surface effects that were interpreted to be liquefaction-related. However, the interpretation of these phenomena at the Pozzone site is not straightforward. Furthermore, the site is characterized by an abundance of fine-grained sediments, which are not typically found in liquefiable soils. Therefore, in this study, we perform a number of detailed stratigraphic and geotechnical investigations (including continuous-coring borehole, CPTu, SDMT, SPT, and geotechnical laboratory tests) to better interpret these 1915 phenomena and to evaluate the liquefaction potential of a lacustrine environment dominated by fine-grained sedimentation. The upper 18.5 m of the stratigraphic succession comprises fine-grained sediments, including four strata of coarser sediments formed by interbedded layers of sand, silty sand and sandy silt. These strata, which are interpreted to represent the frontal lobes of an alluvial fan system within a lacustrine succession, are highly susceptible to liquefaction. We also find evidence of paleo-liquefaction, dated between 12.1–10.8 and 9.43–9.13 kyrs ago, occurring at depths of 2.1–2.3 m. These data, along with the aforementioned geotechnical analyses, indicate that this site would indeed be liquefiable in a 1915-like earthquake. Although we found a broad agreement among CPTu, DMT and shear wave velocity “simplified procedures” in detecting the liquefaction potential of the Pozzone soil, our results suggest that the use and comparison of different in situ techniques are highly recommended for reliable estimates of the cyclic liquefaction resistance in lacustrine sites characterized by high content of fine-grained soils. In geologic environments similar to the one analysed in this work, where it is difficult to detect liquefiable layers, one can identify sites that are susceptible to liquefaction only by using detailed stratigraphic reconstructions, in situ characterization, and laboratory analyses. This has implications for basic (Level 1) seismic microzonation mapping, which typically relies on the use of empirical evaluations based on geologic maps and pre-existing sub-surface data (i.e., age and type of deposits, prevailing grain size, with particular attention paid to clean sands, and depth of the water table).

The control of earthquake sequences on hillslope stability

AbstractEarthquakes trigger landslides in mountainous regions. Recent research suggests that the stability of hillslopes during and after a large earthquake is influenced by legacy effects of previous seismic activity. However, the shear strength and strain response of ductile hillslope materials to sequences of earthquake ground shaking of varying character is poorly constrained, inhibiting our ability to fully explain the nature of earthquake‐triggered landslides. We used geotechnical laboratory testing to simulate earthquake loading of hillslopes and to assess how different sequences of ground shaking influence hillslope stability prior to, during, and following an earthquake mainshock. Ground‐shaking events prior to a mainshock that do not result in high landslide strain accumulation can increase bulk density and interparticle friction. This strengthens a hillslope, reducing landslide displacement during subsequent seismicity. By implication, landscapes in different tectonic settings will likely demonstrate different short‐ and long‐term responses to single earthquakes due to differences in the magnitude, frequency, and sequencing of earthquakes.

Geomechanical characterization of some adobe materials

The influence of the material properties in the physical and numerical modelling of historical buildings suggests identifying proper laboratory procedures for their mechanical characterization. In the following some aspects are discussed of the geotechnical laboratory tests suitable for the characterization of some adobe materials used in historical heritage.Apart from the conventional identification and classification procedures, the direct shear and the uniaxial compression tests are considered. The study intends to provide additional experimental information that could be used in subsequent studies for the development of constitutive laws applicable in the numerical analysis aimed, for instance, at comparing the effectiveness of various alternative solutions applicable in the field for the restoration of buildings that characterize monument sites.

La Pintada landslide—A complex double-staged extreme event, Guerrero, Mexico

AbstractExtreme storms commonly trigger landslides in regions of humid, warm tropical climate causing loss of life and economic devastation. The tropical mountainous areas of Guerrero in southwest Mexico are frequently hit by extreme hurricanes and cyclones and thus prone to landslides. On 16 September 2013, a huge landslide resulted in 71 fatalities and destroyed a large part of La Pintada Village. We applied remote sensing techniques using the LIDAR DEM and high-resolution images of the La Pintada area, a post-landslide field survey, geotechnical laboratory tests of colluvium material from the landslide, and a slope stability analysis. We also interviewed eyewitnesses accounts of the event. Our results suggest that the 2013 La Pintada landslide was a complex and two-stage event. An intense four-day-long rainfall event related to the landfall of Hurricane Manuel resulted in the oversaturation of soil, which was the main factor that caused the landslide. The effect of rainfall was amplified by the lack of...

Effects of oxidation on residual shear strength of shales within Lea Park Formation

The residual shear strength of Cretaceous Lea Park Formation shale near Lloydminster, Saskatchewan, was evaluated to determine its suitability for road construction. Exposure of these shales results in oxidation, leaching, and other geochemical changes, which may affect the physicochemical forces that control the shear strength behaviour. A laboratory geotechnical testing program was complemented with geochemical testing and modelling. In situ pore-water chemistry and cation-exchange site composition were determined from soil-water extracts using an equilibrium geochemical model. It was found that leaching by low ionic strength recharge removes dissolved and adsorbed sodium from surficial deposits. Sulfur oxidation overprinted the effects of leaching by releasing acidity and sulfate, increasing stored gypsum, and increasing dissolved and adsorbed magnesium. Shear testing indicated higher apparent residual friction angles for surficial samples with lower exchangeable sodium; however, this relationship is obfuscated by the impact of increased sand contents on increased strength. Samples at depth exhibited lower apparent residual friction angles with higher clay fractions and greater exchangeable sodium. Fully assessing the long-term stability of the material would require further laboratory testing, and a theoretical basis to link the geochemical model results to the calculation of physicochemical forces in multi-ion, multi-mineral systems. Qualitatively, it can be concluded that near-surface oxidized and leached shales have greater shear strength, with less risk of this strength changing as a result of post-construction weathering.

Determination of aquifer hydrodynamic parameters: a key tool for the design of an Open-loop Groundwater Heat Pump System

Open-loop groundwater geothermal heat pumps (GWHP) represent an interesting technology that is expected to contribute significantly to the reduction of primary energy use for buildings heating and cooling needs especially in urban context. In the GWHP's design phases the geological and hydrogeological parameters must be accurately determined in order to maximize efficiency and minimize installation costs.Physical properties of the aquifer such as the porosity and the thermal parameters of the aquifer framework have been usually obtained through field and laboratory geotechnical testing. Hydrogeological and hydraulic parameters of the exploited aquifer such as hydraulic conductivity and the storativity are usually obtained through pumping test.As reported in literature, the prevailing component of the heat transfer in the aquifer induced by the water re-injection is related to the advection and therefore the determination of the real field groundwater velocity in transient and steady conditions is fundamental in the modelling of the thermal plume especially in the GWHP plant design phases. To this aim the pumping tests appear to be among the most useful field hydrogeological investigations to be performed in most cases. Such tests can also provide suitable information related to the aquifer productivity (specific discharge rate) and therefore can permit to assess if the GWHP plant requirement can be satisfied in terms of groundwater sustainable withdrawals. A real field pilot plant aimed to supply energy needs to the Architecture Faculty building of the Politecnico di Torino (NW Italy) is presented and discussed.

Backbone curves with physical parameters for passive lateral response of homogeneous abutment backfills

Recent advances in performance-based seismic assessment and design of bridges call for the development of computationally efficient models with high fidelity for nonlinear static pushover and transient dynamic analyses. Response models of bridge abutment systems are significant ingredients of such analyses. Herein, we present closed-form relationships for lateral response of abutment backwalls with uniform backfills. These relationships are obtained by performing extensive parametric studies with a previously validated limit-equilibrium model coupled with hyperbolic soil stress–strain relations. The resulting “Generalized Hyperbolic Force–Displacement (GHFD)” backbone curve has explicit dependencies on the physical properties of the abutment system, including the backwall height. All input parameters to the GHFD relationships are measurable via standard geotechnical laboratory tests. We also perform a validation study using published measurements from several field and laboratory experiments. The GHFD equations are in closed form and can easily be implemented in a structural analysis package as a nonlinear spring that accounts for the bridge abutment–backfill interaction.

Influence of Spatial Variation in Subgrade Properties on the Design of Highway Flexible Pavements

Influence of spatial variation in subgrade properties on the integrity of highway pavement design is the burden of this research. Interruption, delay and discomfort in transportation flow that characterize roads across the globe due to poor pavement conditions are pathetic experiences. This work is an attempt to investigate the influence of subgrade variation on the design thicknesses of highway flexible pavements, using subgrade properties and traffic characteristics encountered along the Enugu-Onitsha expressway. Soil samples collected from selected sections of the expressway were subjected to geotechnical laboratory tests like particles size distribution, Atterberg’s limits, compaction and California bearing ratio in order to analyse their properties. The results generated from these three samples from different stations across the road showed that the soil materials along the Enugu-Onitsha expressway vary significantly. Sample from Nkpor, Awkuzu and Kwata stations contain 15%, 45% and 80% fines (silt and clay) respectively, likewise their MDD and OMC are 1852KN/m3, 1980KN/m3 and 1788KN/m3; 11.7%, 11%, and 14.6% respectively. The 48 hour soaked CBR values of soil samples from Nkpor and Awkuzu stations are 8% and 9% respectively while Kwata station is 2.3%. The plasticity index and liquid limit results were also 11%; 31% and 9%; 27.4% for Awkuzu and Kwata samples while Nkpor sample in a non-plastic soil. Based on ASSHTO classification, the soils fall within A-2-4, A-6 and A-4 categories which depicted a significant variation in properties, fair to bad. Based on the design outputs for pavement thicknesses, it was concluded that designing a length of highway with a single CBR value will be uneconomical for areas with significantly higher surface modulus as well as providing insufficient thicknesses for areas with lower actual CBR than the observed. Sectional pavement design at not more than 1km intervals was recommended.

The influence of natural reinforcement fibers, gypsum and cement on compressive strength of earth bricks materials

This paper presents an experimental work on the compressive strength of earth bricks in particular the influence of additives. In total 21 different test series are carried out with different composition of earth, cement, gypsum, hemp and flax fibers. The earth material is characterized by geotechnical laboratory tests. The test results indicated that the compressive strength is highly dependent on the density of the bricks. The fibers hemp and flax have rather low impact on the compressive strength of earth bricks, but they have strong influence on the breaking behavior. Cement and gypsum as additive, as they seem to reduce the binding force of the clay minerals, lead to a highly decreased strength.

A new index for evaluating liquefaction resistance of soil under combined cyclic shear stresses

In geotechnical laboratory testing, a cyclic sine wave loading is applied to samples to simulate seismic loading. The shear stress amplitude in cyclic tests, the cyclic stress ratio (CSR) is always used to express the resistance of soil to cyclic loading. However, the cyclic strength of samples subjected to different cyclic stress patterns can exhibit quite differently. Apart from the possibility of the continuous rotation of the principal stress direction, the difference in shear stress due to cyclic changes induced by different cyclic stress paths is also an influential factor. A new parameter is presented in this paper, the equivalent cyclic stress ratio (ESR), which is defined as the ratio of the mean value of the maximum shear stress in a cycle to the initial effective confining pressure. With the hollow cylinder apparatus, several series of cyclic loading tests were carried out on Fujian fine sand and Qiantang silt. The ESR-based data all fall within a very narrow band in the half logarithmic coordinate, even when cyclic stress paths are different. Test results from Ishihara on Toyoura sand were also re-analyzed using the new index, and a similar correlation was evidenced for loose sand under various cyclic stress paths. For dense and very dense sands, the treatment can also narrow the discreteness of results. With this new index, the cyclic strength of soil obtained from relatively simple tests, e.g. cyclic triaxial tests or cyclic torsional shear tests can be easily used to predict the cyclic strength of soil subjected to combined cyclic shear stresses.

Geotechnical Properties of LAPONITE RD®

This paper presents a synthetic smectite clay comparable in structure to the natural clay mineral hectorite that can be used in physical geotechnical models as a transparent soft clay surrogate. Upon dispersion with distilled water, the synthetic clay hydrates and swells, forming a transparent slurry that can then be consolidated. The transparency of the resulting consolidated slurry allows for non-intrusive observation of behavior within a physical model. Observations possible within the physical model include visualizing flow and the measurement of deformation using nonintrusive optical visualization techniques including digital image correlation. Initial synthetic clay concentrations from 4 to 4.5 % by weight were examined. These initial concentrations were further consolidated resulting in samples with higher concentrations by weight for use in various geotechnical laboratory tests. Due to the potential of the synthetic clay to be a soft clay surrogate, geotechnical laboratory testing typically used to characterize soft clays was performed on the solidified colloidal slurry including a series of laboratory vane tests, consolidation tests, and a series of permeability tests. In addition to the geotechnical testing, physical properties of the synthetic clay were examined and results from the geotechnical testing are presented in conjunction with the physical properties and sample preparation methods. Results of the geotechnical laboratory tests demonstrate that the synthetic clay exhibits macroscopic geotechnical properties comparable to soft cohesive soils and therefore can be used as a soft clay surrogate for use in geotechnical physical model testing, particularly those related to offshore geotechnics.

Performance assessment of a bentonite–sand mixture for nuclear waste isolation at the potential Akkuyu Nuclear Waste Disposal Site, southern Turkey

This study assesses the geotechnical performance of a compacted bentonite–sand mixture with a bentonite content ranging from 15 to 30 % by weight to be used as a material component in a waste sealing system. Geotechnical laboratory tests such as compaction, falling head permeability, swelling, unconfined compression and shear strength tests were conducted to select an optimum mixture which eventually led to a recommendation to select an optimum bentonite–sand mixture possessing a bentonite content of 30 % for the isolation of underground waste disposal facilities. Bentonite–sand seal design was performed for the optimum seal selected as a function of the axial stress applied to the seal and seal length-to-radius ratio.

The role of weathering in the initiation and mobility of a rare complex avalanche at the Nigeria–Cameroon border, West Africa

A catastrophic rock debris avalanche on one of the highlands demarcating Cameroon and Nigeria, 3 days after a transient period of heavy rainfall in November 2010, killed two people and damaged economic trees, plants and farmlands. Detailed field investigation and sampling were undertaken by a team from the International Programme on Landslide to analyse the slope movement. The investigation was in two phases—5 days and then 7 months after the event to study the effect of alternating dry and rainy seasons on the geotechnical properties of the materials associated with the slope failures. It was also aimed at assessing the effect of time on the morphology of the slip plane as a new approach to understanding the development of potential failure planes and reactivated landslides. Available evidence showed that present failure planes form mini-deposition axes which may become future slip zones as they are still steep enough to accelerate instability. The research also traced the pattern of rock weathering and joints evolution in the area and found that the systematic weathering of feldspar in the basement aggravated slope instability by creating zones of weakness characterized by structures that aid fragmentation. Soils were thin ( 2 m) in others and may represent the differential effect of weathering and erosion on the mountains which are important in analyzing the mechanism and mobility of the failed masses. Samples collected were subjected to various geotechnical laboratory tests such as unconsolidated undrained triaxial, consistency, particle size and permeability tests.

Site Investigation Of Road Drains For Rural Road On Batu Pahat Soft Clay (BPSC)

Road failures may be caused by many factors. In Batu Pahat district, open channel system is adopted and built on Batu Pahat Soft Soil and may be a crucial factor to probable damage of the rural roads structure. This study is focused on the drainage system for rural roads in Parit Raja, Batu Pahat. The type of damages is observed and the causes are identified. Recommendations on the best method are made to improve the effectiveness of current drainage system. Both site and laboratory geotechnical testing are carried out to analyze the causes of failure to the drainage system. Laboratory testing such as sieve analysis, moisture content, Atterberg limit, specific gravity and shear strength are conducted. While Mackintosh probes testing and vane shear test are conducted for site testing. From the analysis, four categories of drainage failure such as soil movement, edge drop, cracking and erosion due to the characteristics of soft clay that have low shear strength and high compatibility, have been determined. The propose methods to increase the effectiveness of the drainage system are to stabilize the soil using geotextiless, combination geotextiless and geocontainers, soil anchor and lime.