Research PaperEvaluation of dynamic compaction to improve saturated foundation based on the fluid-solid coupled method with soil cap model
Introduction
Dynamic compaction is a common and economical ground improvement technique, which has been widely applied in various types of soil including loosely packed sand (Mayne et al., 1984), silt (Yingren et al., 1998, Nashed, 2006), clayey soil (Menard and Broise, 1975), landfill waste (Van Impe and Bouazza, 1997) and even collapsible loess in their dry/moist states (Feng et al., 2015). Therefore, current researches mainly focus on the DC treatment on dry soils to estimate the dynamic stress distribution (Mayne and Jones, 1983, Michalowski and Nadukuru, 2012, Scott and Pearce, 1975); crater depth (Mullins et al., 2000, Feng et al., 2010, Feng et al., 2013) and influencing depth (Feng et al., 2015, Feng et al., 2015). However, at some coastal areas, dynamic compaction is also reported to extend its usage to reinforce the foundation with high groundwater table, such as offshore land reclamation and airport construction (Wang et al., 2019). As a matter of fact, a high proportion of the dynamic impact is first transferred to the pore water, and the densification effectiveness for saturated deposit is dominated by the soil permeability that controls the dissipation speed of excess pore water pressure (Ghassemi et al., 2010, Lukas, 1995). Consequently; in order to obtain reasonable design parameters of dynamic compaction against the high groundwater table, it is necessary to examine the effects of soil permeability and groundwater table on the dissipation of excess pore water and development of effective soil stress and void ratio.
Biot pointed that relative motion existed between soil skeleton and pore fluid even when there is no drainage of pore fluid. Hence, the well-known dual-phase formulations were proposed to describe solid–fluid interaction by inertial, viscous and volumetric coupling under dynamic loads (Biot, 1956, Biot, 1956). Ghassemi et al. (2010) modelled a fully-coupled analysis of dynamic compaction using the u(displacement of the soil skeleton)–p(pore pressure) formulation on granular soils. They revealed that most of the DC improvement occurred during the undrained phase at the initial stage, and high oscillation of pore pressure appeared. Results also indicated that the improvement zone diminished when the degree of saturation increased. Although the u-p formulation is sufficient for lower-frequency problems, López-Querol et al. (2008)) found that since the u–p formulation neglected the relative fluid acceleration, it lacked accuracy in the computation of excess pore water pressure compared with the u–w(displacement of pore fluid) formulation. In order to overcome this problem, Ye et al. (2014)) developed an implementable method for fully coupled u–U type analysis using ABAQUS software. The solid and pore fluid phases were realized by two overlapping meshes with collocated elements and nodal points. A three-dimensional elasto-plastic model involving impulsive surface loading on dry sand overlying saturated sand was validated to analyze the dynamic compaction problem. The numerical results highlighted the importance role of the slow dilatational wave in dynamic compaction process. Furthermore, the soil should be sufficiently permeable and the loading duration sufficiently long for the slow wave to be more effective. Nevertheless, most numerical simulations of dynamic compaction focused on sandy soils using elastic or simple soils constitutive relationships without plastic flow rules. Additionally, considering the important effect of soil permeability at the situation of high saturation, a series of dewatering techniques, such as prefabricated vertical drains(PVD) (Wang et al., 2000) and vibro-stone columns (Shenthan et al., 2004); have been proposed for densification of saturated low-permeability soils. Cao and Wang (2007) confirmed an effective practice of heavy tamping after rockfilling displacement to improve seabed sediments in coastal reclamation area. Thevanayagam et al. (2009) studied the compaction processes and concurrent densification on the basis of the energy principle method, and concluded that the use of wick drains can greatly enhance densification and depth of improvement in non-plastic silty sands. Although increasing soil permeability is beneficial to improve foundation by dynamic compaction, its suitability to the soil types and groundwater tables is still ambiguous.
The objective of this paper is to develop a fully coupled fluid–solid model to simulate dynamic compaction for various soil types, especially for fine soils with large plastic deformation. Therefore, a dynamic fluid–solid coupled FE method was first proposed to reveal the elastic, viscous and plastic behaviors during the dynamic compaction process in saturated soil. The Biot’s dynamic u–U–p formulation was employed to describe the coupling of pore fluid and solid phases, which was discretized into finite elements by application of the Galerkin method and viscous Cartesian connectors. The soil behavior was simulated based on the cap yield hardening model with the principle of effective stress, which was programmed as a subroutine into the ABAQUS software. A comprehensive comparison between the proposed method and previous analytical solutions and field measurement was performed, which showed reasonably good agreement. Then the proposed fluid–solid coupled FE method was used to evaluate the improvement effect of dynamic compaction on saturated foundation considering various groundwater tables and soil types. Some engineering solutions were also suggested to effectively improve the fine soil foundation with high groundwater tables.
Section snippets
Biot’s dynamic u–U/u–U–p formulation
Biot (Biot, 1956, Biot, 1956) proposed the well-known u-U-π formulations together with the elastic constitutive relations to solve the three dimensional solid–fluid coupled problems under dynamic loading. By introducing the effective stress principle, the u-U-π formulation can be converted to the u-U-p formulation, which iswhere denotes the directional derivative matrix; and denote the effective stress and pore pressure macroscopically; ,
Validation of the fluid–solid coupled method with linear elastic model
Firstly, the implementation of the fluid–solid coupled model on ABAQUS is verified with simple linear elastic soil model. Hiremath et al. (Hiremath et al., 1988) deduced analytical solutions for the problem of a fully saturated porous layer with a finite thickness subjected to velocity loading. The soil column is 0.5 m long and the bottom boundary is rigid and impermeable as illustrated in Fig. 1. Two plane-strain overlapping meshes are used, namely, the solid mesh and the fluid mesh, each
Numerical analysis
In this section, the effects of groundwater table and soil permeability on the DC improvement are analyzed based on the proposed numerical model as shown in Fig. 5. Results on four different groundwater tables, i.e., h = 0 m, 2 m, 4 m and 6 m below ground surface, are compared with those of dry soil foundation. The soil permeability coefficients used in the analysis are k = 10−2 m/s, 10−3 m/s, 10−5 m/s and 10−7 m/s, representing gravel, coarse sand, silt and silty clay, respectively.
Conclusions
This study investigates the potential application of dynamic fluid–solid coupled FE method with cap model used for the study of dynamic response characteristics on the saturated foundation under dynamic compaction. The proposed numerical model shows reasonably good agreement with the published analytical solutions of one-dimensional transient loading problems and field measurement of dynamic compaction. The effects of groundwater table and soil permeability are examined via the development of
CRediT authorship contribution statement
Zhou Chong: Methodology, Software, Validation, Writing - original draft. Jiang Hongguang: Conceptualization, Methodology, Formal analysis, Writing - review & editing. Yao Zhanyong: Conceptualization, Supervision, Project administration. Li Hui: Software, Validation. Yang Chenjun: Software, Investigation. Chen Luchuan: Project administration, Funding acquisition. Geng Xueyu: Conceptualization, Writing - review & editing.
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.
Acknowledgements
Financial supports from the National Natural Science Foundation for Young Scientists of China (Grant No. 51608306), Shandong Transportation Science and Technology Foundation (2016B20, 2019B47_2), and Young Scholar Future Plan Funds of Shandong University are gratefully acknowledged.
References (39)
- et al.
Densification of desert sands by high energy dynamic compaction
Eng. Geol.
(2013) - et al.
Field study on the reinforcement of collapsible loess using dynamic compaction
Eng. Geol.
(2015) - et al.
Numerical study of the coupled hydro-mechanical effects in dynamic compaction of saturated granular soils
Comput. Geotech.
(2010) - et al.
Unified dynamic shear moduli and damping ratios of sand and clay
Soil Found.
(1993) - et al.
Prediction of dynamic compaction pounder penetration
Soils Found.
(2000) - et al.
Investigation on the dynamic liquefaction responses of saturated granular soils due to dynamic compaction in coastal area
Appl. Ocean Res.
(2019) - et al.
Dual-phase coupled u–U analysis of wave propagation in saturated porous media using a commercial code
Comput. Geotech.
(2014) Theory of propagation of elastic waves in a fluid-saturated porous solid. I. Low-frequency range
J. Acoust. Soc. Am.
(1956)Theory of propagation of elastic waves in a fluid-saturated porous solid. II. Higher frequency range
J. Acoust. Soc. Am.
(1956)- et al.
Seabed ground improvement in coastal reclamation area by heavy tamping after rockfilling displacement
Mar. Georesour. Geotechnol.
(2007)
Nonlinear Analysis in Soil Mechanics: Theory and Implementation
Material model for granular soils
J. Eng. Mech.
Elimination of loess collapsibility with application to construction and demolition waste during dynamic compaction
Environ. Earth Sci.
Field studies of the effectiveness of dynamic compaction in coastal reclamation areas
Bull. Eng. Geol. Environ.
Dynamic compaction of ultra-high energy in combination with ground replacement in coastal reclamation areas
Mar. Georesour. Geotechnol.
Ground response to dynamic compaction of dry sand
Géotechnique
Analysis of one-dimensional wave propagation in a fluid-saturated finite soil column
Int. J. Numer. Anal. Meth. Geomech.
Dynamic Properties of Soils
Method for estimating dynamic compaction effect on sand
J. Geotechn. Geoenviron. Eng.
Cited by (19)
A review of advances in mechanical behaviors of the underground energy transmission pipeline network under loads
2023, Gas Science and EngineeringParameters of dynamic compaction based on model test
2023, Soil Dynamics and Earthquake EngineeringVibration safety evaluation and vibration isolation control measures for buried oil pipelines under dynamic compaction: A case study
2023, Soil Dynamics and Earthquake EngineeringEffect of dynamic compaction by multi-point tamping on the densification of sandy soil
2022, Computers and GeotechnicsCitation Excerpt :The performance of this procedure is assessed via application to three cases of DC in the field. The soil model used in this study is a cap model with a non-hardening shear yield surface and hardening cap, which has been widely used for modelling soil behaviour under DC (Gu & Lee, 2002; Lee & Gu, 2004; Yao et al., 2018; Zhou et al., 2020), Fig. 1. in which D' and W' are volumetric hardening coefficients obtained from odometer tests (Chen & Mizuno, 1990), and p'0 is the in-situ mean effective stress.
Intelligent monitoring method for tamping times during dynamic compaction construction using machine vision and pattern recognition
2022, Measurement: Journal of the International Measurement ConfederationCitation Excerpt :Worldwide, the DCM is used in airports, highways and other large-scale foundation treatment projects [5–8]. Since Menard proposed the DCM in 1970 s [9], many researchers have investigated its compaction mechanism and influencing factors [1–3,5–8,10–15]. These studies show that the tamping times, tamping energy and tamping pit layout are the key parameters of the DCM construction quality [2,8,11,12,16–18].
Research on flexible unloading method for dynamic compaction
2021, Journal of Building EngineeringCitation Excerpt :The seismic wave generated by tamping is a phenomenon of concern in construction engineering. By analyzing the dynamic contact between the heavy hammer and the ground [4], simulating the dynamic stress distribution on the ground during impact [5] and foundation deformation [6,7], it is found that most of the impact energy of the hammer propagates underground and a small part of the impact energy is transformed into seismic wave and sound energy [8,9]. By measuring the vibration of the ground with 1200kN⋅m tamping energy [10], it is found that the vibration speed decreases significantly beyond 4 m from the center of the tamping point.