3D DEM simulation of initial anisotropy in dredger fill soft soil

Abstract. Large-scale land subsidence often occurs after large-scale land formation caused by dredger fill, which affects the sustainable development of the region. In order to prevent and control land subsidence in the area with dredger fill, the characteristics of land subsidence and its main influencing factors need to be studied. A typical region was examined using geological survey data, land-level monitoring and comparative analysis, to provide insight regarding the variability of dredger-fill characteristics and impacts on land subsidence. The geological survey results provided the information about burial distribution characteristics of dredger fill and its underlying soil layers. The land-level monitoring results were analyzed to characterize the spatial–temporal distribution of land subsidence. The comparative analysis of land subsidence with the formation time, soil properties, thicknesses of dredger fill and the lower soft soil layer provided information about the different impacts. The monitoring results show that the land subsidence of dredger fill areas was substantially larger than that of adjacent areas. The later the filling was formed, the thicker the filling is, and the more clay-rich the soil property and the thicker the soft soil layer is, the larger the land subsidence is. Finally, the future trend of land subsidence in the study area are given and some suggestions on the prevention and control of land subsidence are also given.

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Basic set of experiments for determination of mechanical properties of sand

Bulletin of the Polish Academy of Sciences Technical Sciences ◽

10.2478/bpasts-2014-0015 ◽

2014 ◽

Vol 62 (1) ◽

pp. 129-137

Author(s):

A. Sawicki ◽

J. Mierczyński

Keyword(s):

Mechanical Properties ◽

Soil Mechanics ◽

Physical And Mechanical Properties ◽

Local Strain ◽

Initial State ◽

Laboratory Equipment ◽

Additional Information ◽

Basic Set ◽

Initial Anisotropy

Abstract A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.

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Application of geotextiles in strengthening soft soil foundation

Advance in Civil Engineering ◽

10.35534/ace.0101004c ◽

2019 ◽

Vol 1 (1) ◽

pp. 18-22

Author(s):

Yang Xueqing ◽

Zhong Xiang

Keyword(s):

Soft Soil ◽

Soil Foundation ◽

Soft Soil Foundation

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Strength Performance and Microstructure of Calcium Sulfoaluminate Cement-Stabilized Soft Soil

Sustainability ◽

10.3390/su13042295 ◽

2021 ◽

Vol 13 (4) ◽

pp. 2295

Author(s):

Hailong Liu ◽

Jiuye Zhao ◽

Yu Wang ◽

Nangai Yi ◽

Chunyi Cui

Keyword(s):

Soft Soil ◽

Hydration Product ◽

X Ray Diffraction ◽

Calcium Sulfoaluminate Cement ◽

Strength Performance ◽

X Ray ◽

Calcium Sulfoaluminate ◽

Stabilized Soil ◽

Calcium Silicates ◽

Hydrated Calcium

Calcium sulfoaluminate cement (CSA) was used to stabilize a type of marine soft soil in Dalian China. Unconfined compressive strength (UCS) of CSA-stabilized soil was tested and compared to ordinary Portland cement (OPC); meanwhile the influence of amounts of gypsum in CSA and cement contents in stabilized soils on the strength of stabilized soils were investigated. X-ray diffraction (XRD) tests were employed to detect generated hydration products, and scanning electron microscopy (SEM) was conducted to analyze microstructures of CSA-stabilized soils. The results showed that UCS of CSA-stabilized soils at 1, 3, and 28 d firstly increased and then decreased with contents of gypsum increasing from 0 to 40 wt.%, and CSA-stabilized soils exhibited the highest UCS when the content of gypsum equaled 25 wt.%. When the mixing amounts of OPC and CSA were the same, CSA-stabilized soils had a significantly higher early strength (1 and 3 d) than OPC. For CSA-stabilized soil with 0 wt.% gypsum, monosulfate (AFm) was detected as a major hydration product. As for CSA-stabilized soil with certain amounts of gypsum, the intensity of ettringite (Aft) was significantly higher than that in the sample hydrating without gypsum, but a tiny peak of AFm also could be detected in the sample with 15 wt.% gypsum at 28 d. Additionally, the intensity of AFt increased with the contents of gypsum increasing from 0 to 25 wt.%. When contents of gypsum increased from 25 to 40 wt.%, the intensity of AFt tended to decrease slightly, and residual gypsum could be detected in the sample with 40 wt.% gypsum at 28 d. In the microstructure of OPC-stabilized soils, hexagonal plate-shaped calcium hydroxide (CH) constituted skeleton structures, and clusters of hydrated calcium silicates (C-S-H) gel adhered to particles of soils. In the microstructure of CSA-stabilized soils, AFt constituted skeleton structures, and the crystalline sizes of ettringite increased with contents of gypsum increasing; meanwhile, clusters of the aluminum hydroxide (AH3) phase could be observed to adhere to particles of soils and strengthen the interaction.

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Checking the site categorization criteria and amplification factors of the 2021 draft of Eurocode 8 Part 1–1

Bulletin of Earthquake Engineering ◽

10.1007/s10518-021-01118-9 ◽

2021 ◽

Author(s):

Roberto Paolucci ◽

Mauro Aimar ◽

Andrea Ciancimino ◽

Marco Dotti ◽

Sebastiano Foti ◽

...

Keyword(s):

Numerical Simulations ◽

Shear Wave ◽

Ground Motion ◽

Shear Wave Velocity ◽

Soft Soil ◽

Site Amplification ◽

Soil Conditions ◽

Eurocode 8 ◽

Site Specific ◽

Amplification Factors

AbstractIn this paper the site categorization criteria and the corresponding site amplification factors proposed in the 2021 draft of Part 1 of Eurocode 8 (2021-draft, CEN/TC250/SC8 Working Draft N1017) are first introduced and compared with the current version of Eurocode 8, as well as with site amplification factors from recent empirical ground motion prediction equations. Afterwards, these values are checked by two approaches. First, a wide dataset of strong motion records is built, where recording stations are classified according to 2021-draft, and the spectral amplifications are empirically estimated computing the site-to-site residuals from regional and global ground motion models for reference rock conditions. Second, a comprehensive parametric numerical study of one-dimensional (1D) site amplification is carried out, based on randomly generated shear-wave velocity profiles, classified according to the new criteria. A reasonably good agreement is found by both approaches. The most relevant discrepancies occur for the shallow soft soil conditions (soil category E) that, owing to the complex interaction of shear wave velocity, soil deposit thickness and frequency range of the excitation, show the largest scatter both in terms of records and of 1D numerical simulations. Furthermore, 1D numerical simulations for soft soil conditions tend to provide lower site amplification factors than 2021-draft, as well as lower than the corresponding site-to-site residuals from records, because of higher impact of non-linear (NL) site effects in the simulations. A site-specific study on NL effects at three KiK-net stations with a significantly large amount of high-intensity recorded ground motions gives support to the 2021-draft NL reduction factors, although the very limited number of recording stations allowing such analysis prevents deriving more general implications. In the presence of such controversial arguments, it is reasonable that a standard should adopt a prudent solution, with a limited reduction of the site amplification factors to account for NL soil response, while leaving the possibility to carry out site-specific estimations of such factors when sufficient information is available to model the ground strain dependency of local soil properties.

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Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

Earthquake Spectra ◽

10.1177/8755293020974692 ◽

2020 ◽

Vol 36 (2_suppl) ◽

pp. 213-237

Author(s):

Miguel A Jaimes ◽

Adrián D García-Soto

Keyword(s):

Mexico City ◽

Seismic Design ◽

Soft Soil ◽

Response Spectra ◽

Elastic Model ◽

Ground Acceleration ◽

Nonstructural Components ◽

Floor Response Spectra ◽

Instrumented Buildings ◽

Floor Acceleration

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

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