Characterization of elastic and shear moduli of adapazari soils by dynamic triaxial tests and soil-structure interaction with site properties
Introduction
The Kocaeli earthquake, with a large magnitude of Mw = 7.4, originating at a 17 km depth along the North Anatolian Fault system in Turkey occurred around 3:05 a.m. on the 17th of August in 1999. The fault breaking due to a right-lateral strike slip generated an immense fault rupture which continued throughout a line more than 100 km length [1]. This earthquake, also called the İzmit earthquake, inflicted heavy structural destruction on more than half of the existing buildings some of which totally collapsed. Hence, unfortunately around twenty-thousand human lives were lost in Adapazari and in the surrounding area. A large number of reinforced concrete structures, most of which were 3–5 story buildings, penetrated the bearing ground soil and sunk down into the earth or tilted due to liquefaction and loss of soil strength. Most of these buildings also had significant structural damage [2].
Various researchers have studied the effects of the characteristics and conditions of the foundation soil and subsurface layers further below on the structural damage of the load-carrying frame and on the occurrence of ground failure caused by the earthquake by liquefaction assessments and by one-dimensional site response analyses [[3], [4], [5], [6], [7], [8], [9], [10]]. The results of all of these studies indicate that distinct differences in the properties of recent deposits in and around Adapazari have a major contribution to the ground failure occurrences and to the structural damage due to the earthquake.
Researchers [[11], [12]] investigated the liquefaction susceptibility and the stress-strain behavior for fine grain size soils conducting an array of conventional static triaxial tests and stress-controlled undrained cyclic triaxial loading tests on intact soil core specimens. The results of the tests performed by Ref. [11] indicated that the soils specimen did not exhibit any peculiarities for the evaluation of liquefaction as far as the low-strain (stiffness) and the large-strain (strength) behaviors are considered [13,14]. Conducted many cyclic direct simple shear tests with the purpose of evaluating the properties of Adapazari soils under dynamic conditions, including different classes of soils. Similarly, tests performed by Ref. [12] indicated some soil types with low plasticity index (PI) less than 12, having a water content (wn) to liquid limit (LL) greater than 0.85 (wn/LL > 0.85) was susceptible to liquefaction under a sequel of significant cyclic loadings.
Comparison of the results for the dynamic properties of the soils determined by the seismic field tests and those by the laboratory measurements are important in tackling earthquake engineering problems from geotechnical aspects. It is also necessary to determine the shear modulus and the damping ratio values when the shear strains are larger than the strains from which the greatest shear modulus is obtained in the field. These values are required to evaluate the soil-structure interaction problems, and, at the same time, dynamic behavior of the soils. Yet, the shear modulus under dynamic loading is significantly important in the seismic design of geotechnical systems, and nonlinear shear deformations in soil material yields deterioration in the shear modulus (G).
G is usually normalized by a maximum shear modulus in very low strain level (Gmax). The small-strain or, in other words, the maximum shear modulus (i.e., G0 or Gmax, respectively) within elastic boundaries generally corresponds to shear strains (γ) as low as 10−4% (γ < 10−4%) [14,15]. [16,56, 57] experimentally showed that shear modulus and, also, damping ratio of fine soils were dependent on strain rate that soil was exposed in a dynamics triaxial test.
Ghayoomi et al. [17] indicates that properties of soil under dynamic loading conditions are critical in proper design of geotechnical systems against seismic event, and precise anticipation of (G) is vital to assess soil's response to extreme dynamic loads such as earthquakes, wind, ocean waves etc.
Gu et al. [18] conducted some cyclic triaxial loading tests on saturated clays with and without different levels of confining pressure. In the study, it is investigated how normalized shear modulus degradation (G/Gmax) is coupled with cyclic shear stress and cyclic normal stress. It is indicated that properties of G/Gmax under different loading conditions will reflect site condition better than tests conducted considering just one loading. Vipulanandan and Ata [19] investigated the dynamic properties of sodium silicate-grouted sand using cyclic triaxial tests, and found that the dynamic moduli and the damping ratio obtained from the impact-echo method gave reasonable results as compared to cyclic tests. Teachavorasinskun et al. [20] measured the shear modulus and the damping ratio of undisturbed Bangkok clay samples using a cyclic triaxial apparatus, and their results showed that the equivalent shear modulus measured at strains of 0.01% was about 80% of the value obtained from the shear wave velocity measurements. Sharma and Fahey [21] explained the deformation properties of artificially cemented calcareous soil under undrained cyclic triaxial loading conditions with different confining pressure and cyclic stress levels. They observed that if number of cycles was increased, the deviatoric strain and stress at yield were reduced, which resulted in a significant decrease in stiffness. Low plasticity silt's characteristic of degradation in strength and stiffness is investigated by Ref. [22] conducting stress controlled tests in undrained cyclic triaxial loading, which is followed by strain controlled monotonic compressive shear tests on normally consolidated and over-consolidated reconstituted Keuper Marl silt. They showed that cyclic shear strain would be better to correlate post cyclic stiffness degradation of both normally and over-consolidated silt than cyclic-induced excess pore pressure.
The first objective of this study, is to determine the elasticity modulus and the shear modulus values of Adapazarı soils by using a dynamic triaxial test setup. Since the shear modulus (G) cannot be determined directly in the dynamic triaxial test apparatus, first the dynamic modulus of elasticity is determined, and then the shear modulus is calculated indirectly. The second aim of this study is to observe relationships between the elasticity modulus obtained from the stress-strain relationship in the dynamic and static loadings of the test specimens and the axial strain at the end of each cyclic test.
Both types of disturbed and undisturbed soil samples were retrieved from ten boreholes at eight locations spread across different points in Adapazarı neighborhoods. These samples were used to determine the strain-dependent shear modulus under cyclic loading conditions conducted on instruments in the laboratory. Two separate sets of undrained cyclic triaxial loading tests were carried out on samples of undisturbed soil. The cyclic loading during the first set of tests was applied at very small recursive loads and was continued until the pore water pressure (pwp) did not form (γ < 10−4% or pwp ≅ 0). The second set comprised tests using various cyclic stress ratios which were carried out for 20 equivalent cycles (N = 20) and was considered to simulate the Kocaeli earthquake on 17 August 1999.
The results of these dynamic tests performed to observe the strain-dependent shear modulus of undisturbed soils under repeated loading are presented here, which are believed to contribute to the seismic design and structural performance of geotechnical systems in general everywhere in the world.
In addition, a five-story reinforced concrete frame, designed for a site in Adapazari, is analyzed to evaluate effect of a soil profile on superstructure on site. A soil profile is modeled based on triaxial test results of soil samples. Structural frame is modeled as fixed base and with the soil profile, and nonlinear time history analyses for both frames are performed. Maximum inter-story drift ratio of both frames is compared.
Section snippets
Geologic setting and soil conditions on site
A major portion of the settlement area of the city of Adapazari rests on thick alluvial deposits. The General Directorate of State Hydraulic Works (DSI) drilled a deep borehole in the Yenigun District, and bedrock was not observed up to 200 m from the surface. The shallow soils in the superficial layers are substantially recent deposits of ground material eroded, conveyed, and established by the Cark and Sakarya rivers. These rivers often flooded land until flood-control structures were built a
Characteristics of soil in adapazari
Ten bore holes, which were not too far apart from each other and located in those areas with and without soil failure, were drilled in the city of Adapazari to investigate the subsurface conditions, SPTs were performed. Every borehole soil specimen was taken down to as low as 20 m depth, depending on soil layer thickness. To ensure good quality data, the procedures outlined in relevant ASTM standards were carefully implemented [24]. All of the boreholes, except one, were drilled in eight
Test program
Both types of disturbed and undisturbed soil samples were retrieved from ten boreholes at eight locations spread across different points in Adapazarı neighborhoods. These samples were used to determine the strain-dependent shear modulus under cyclic loading conditions conducted on instruments in the laboratory. Two separate sets of undrained cyclic triaxial loading tests were carried out on samples of undisturbed soil. The cyclic loading during the first set of tests was applied at very small
Conducting of cyclic tests
For determination of stress-strain and strength properties of soils under various cyclic loading conditions, the dynamic triaxial testing system is one of the most effective and reliable laboratory tests, and this test is much popular in geotechnical earthquake engineering. Here, we have conducted the cyclic triaxial compression tests with reference based on the Japanese Geotechnical Society Standard [29,30].
The cyclic triaxial test systems in the Soil Dynamics Laboratory of the Istanbul
Determination of the modulus of elasticity
Slope of stress-strain curve is given as modulus of elasticity based on the elasticity theory in the elastic deformation region as depicted by equation (1) below (ε ≤ 10−6). The greatest elasticity moduli were calculated by applying very small cyclic loads so that pore water pressure does not form in the samples under a consolidation pressure of σc' = 100 kPa.
Here, Δσ denotes change in the deviator stress, while the change in the axial small strain is given as Δε.
The values of elastic
Variation of the elastic modulus due to the axial deformation
After very small cyclic loading within the elastic region (ε = 10−5 – 10−6) was applied, experiments were carried out at different dynamic load levels up to Ncyc = 20 cycles on the same specimen without changing the stress and drainage conditions. The modulus of elasticity was calculated during the cyclic loading (ε ≥ 0.1) up to Ncyc = 20 cycles. The curve of the variation in elastic modulus based on axial strain level is illustrated in Fig. 6. As denoted in this figure, although soils were
The shear modulus of soils
Since the shear modulus (G) cannot be determined directly in the dynamic triaxial test systems, it is indirectly calculated after transformations. The equations used are given below.where, E is elasticity modulus, ν is Poisson's ratio.
Axial strains (ε) obtained from the dynamic triaxial test are used for transforming to shear strains (γ) by equation (3) below for undrained conditions (here, ν = 0.5 for silt and clay soils) [[37], [38], [39]]. The Poisson ratio can be taken as 0.5 for
The relationship between the initial elastic modulus and the static strength
This part of the study aims to obtain relationships between the elasticity modulus obtained from the stress-strain relationship in the dynamic and static loadings of the test specimens and the axial strain at the end of each cyclic test.
The first cycle of the dynamic test was considered as the static test and the initial elasticity modulus (EN=1) was calculated for the first cycle, N = 1. Thereafter, the initial elasticity modulus (EN=20) at the end of N = 20 cycles was calculated to represent
Evaluation of soil-structure interaction on adapazari soils using elasticity and shear moduli determined by dynamic triaxial test
A five-story reinforced concrete frame is modeled as fixed base and with the soil profile shown in Fig. 14 to investigate effect of soil-structure interaction on the dynamic response of superstructure. Soil profile is constructed based on Fig. 2 and properties are selected accordingly. Structural model is perimeter frame of a representational residential RC building in Adapazari, and designed for soil profile of ZE, which has shear wave velocity less than 180 m/s, for the seismic event that has
Conclusions
A series of dynamic triaxial tests were conducted along with relevant static tests with the objective of determining the elasticity modulus and the shear modulus of Adapazarı soils. The main conclusions are as follows:
- 1.
The largest modulus of elasticity is determined at very small deformation levels. And, the stiffness of the sample decreases with increasing number of cycles during the cyclic loading up to N = 20 cycles. The modulus of elasticity in the plastic region also is experimentally
CRediT authorship contribution statement
Zulkuf Kaya: Conceptualization, Methodology, Software, Validation, Data curation, Writing – original draft, Investigation. Ayfer Erken: Conceptualization, Methodology, Writing – review & editing, Investigation, Supervision. Huseyin Cilsalar: Writing – original draft, Software, Visualization.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors would like to thank Japan International Cooperation Agency for the financial support provided by the Turkey–Japan Earthquake Disaster Prevention Center Project (1993–2002).
References (55)
- et al.
Correlation between ground failure and soil conditions in Adapazari, Turkey
Soil Dynam Earthq Eng
(2002) - et al.
Bedrock structure in Adapazari, Turkey- A possible cause of severe damage by the 1999 Kocaeli earthquake
Soil Dynam Earthq Eng
(2002) - et al.
Liquefaction-induced ground deformations at hotel Sapanca during Kocaeli (Izmit), Turkey earthquake
Soil Dynam Earthq Eng
(2002) - et al.
Liquefaction-related building damage in Adapazari during the Turkey earthquake of August 17, 1999
Eng Geol
(2003) - et al.
Two-dimensional nonlinear site response analysis of Adapazari plain and predictions inferred from aftershocks of the Kocaeli earthquake of 17 August 1999
Soil Dynam Earthq Eng
(2004) - et al.
Coastal failures during the 1999 Kocaeli earthquake in Turkey
Soil Dynam Earthq Eng
(2004) - et al.
Undrained cyclic shear and deformation behavior of silt-clay mixtures of Adapazarı, Turkey
Soil Dynam Earthq Eng
(2004) - et al.
Stiffness degradation of natural fine grained soils during cyclic loading
Soil Dynam Earthq Eng
(2007) - et al.
Effect of cyclic loading on monotonic shear strength of fine-grained soils
Eng Geol
(2007) - et al.
Empirical equations for the prediction of the equivalent number of cycles of earthquake ground motion
Soil Dynam Earthq Eng
(2009)
Cyclic and post-cyclic monotonic behavior of Adapazari soils
Soil Dynam Earthq Eng
Unified dynamic shear moduli and damping ratios of sand and clay
Soils Found
The surface rupture and slip distribution of the 17 August 1999_Izmit earthquake (M 7.4), NorthAnatolian fault
Bull Seismol Soc Am
An overview of local site effects and the associated building damage in Adapazari during the 17 August 1999 Izmit earthquake
Bull Seismol Soc Am
Seismically induced landslide at degirmendere nose, Izmit Bay during Kocaeli (Izmit)-Turkey earthquake
Soil Dynam Earthq Eng
Subsurface characterization at ground failure sites in Adapazari, Turkey
J Geotech Geoenviron Eng
Assesment of the liquefaction susceptibility of fine-grained soils
J Geotech Geoenviron Eng
An Assessment of the dynamic properties of Adapazari soils by cyclic direct simple shear tests
Practical method for utilization of commercial cyclic testing apparatuses for computation of site response in central Adapazari
Soil Dynam Earthq Eng
Geotechnical earthquake engineering
Cyclic triaxial test to measure strain-dependent shear modulus of unsaturated sand
Int J GeoMech
Dynamic modulus characteristics of saturated clays under variable confining pressure
Can Geotech J
Cyclic and damping properties of silicate-grouted sand
J Geotech Geoenviron Eng
Shear modulus and damping of soft Bangkok clays
Can Geotech J
Degradation of stiffness of cemented calcareous soil in cyclic triaxial tests
J Geotech Geoenviron Eng
Postcyclic degradation of strength and stiffness for low plasticity silt
J Geotech Geoenviron Eng
A general assessment of the effects of earthquake on the soil-structure interaction in Adapazari 1999. XV ICSMFE. 76–89
Cited by (8)
Study on seismic stability and performance of reconstruction embankment using geogrid reinforced soil technology
2024, Transportation GeotechnicsDynamic Shear Responses of Combined Contaminated Soil Treated with Nano Zero-Valent Iron (nZVI) under Controlled Moisture
2024, Sustainability (Switzerland)Dynamic shear modulus and damping ratio of saturated soft clay under the seismic loading
2023, Geomechanics and EngineeringComparative analysis of damping ratio determination methods based on dynamic triaxial tests
2023, Earthquake and Structures