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Dynamic compaction (DC) represents a cost-effective method for reinforcing subgrade and is particularly suited to treating large-scale building subgrade. Nevertheless, the effect of DC reinforcement on high groundwater level (HGL) subgrade remains uncertain due to the lack of clarity surrounding the energy transfer mechanism of DC in HGL subgrade. In this paper, an outdoor model test of HGL subgrade was conducted based on the DC method. The temporal evolution of the internal transverse and vertical dynamic stresses in soil under different water levels, energy levels, and tamper weight conditions was monitored, and the DC mechanism of HGL subgrade was described from the perspectives of the dynamic stress waveform, peak development, and attenuation. On this basis, a novel methodology for assessing the extent of subgrade reinforcement through the utilization of impulses was put forth, thereby facilitating a more precise evaluation. The results showed that the HGL is obstructive in DC energy transfer. The peak dynamic stress, depth of impact and maximum impulse per unit area were markedly diminished when tamping the water surface. The study results also recommend that construction could expand the application range of the DC method and provide engineering suggestions for the selection of construction parameters and subsequent building construction. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests were performed to obtain the design parameters before official DC operation. The standard penetration test (SPT), shallow plate-load test (PLT), and deformation investigation were conducted in two improvement regions (A1 and A2) with varying tamping energies. During the deformation test, the depth of the tamping crater for the first two points' tamping and the third full tamping was observed at two distinct sites. The allowable ground bearing capacity at two disparate field sites was at least 360 kPa. The reinforcement depths were 3.5 and 3.2 m in the A1 and A2 zones, respectively. The DC process was numerically analyzed by the two-dimensional particle flow code, PFC2D. It indicated that the reinforcement effect and effective reinforcement depth were consistent with the field data. The coral sand particles at the bottom of the crater were primarily broken down in the initial stage, and the particle-crushing zone gradually developed toward both sides of the crater. The force chain developed similarly at the three tamping energies (800, 1500, and 2000 kJ), and the impact stress wave propagated along the sand particles primarily in the vertical direction. [ABSTRACT FROM AUTHOR]

Purposes To investigate the influence of different tamping methods on the reinforcement effect of sand dynamic compaction, this research has been done from the perspective of soil stress distribution characteristics. Methods The dynamic compaction model test was carried out in the outdoor field to monitor the vertical and radial soil pressures in the soil and falling weight acceleration during tamping process, and the displacements in the soil were analyzed by numerical simulation method. Findings It is concluded that in the construction of dynamic compaction method, the vertical soil pressure waveform is the shock wave waveform or the vibration attenuation wave shape, and the radial earth pressure waveform is the impact waveform; There are two reinforcement modes in the process of dynamic compaction, the soil under tamping point is mainly vertically compacted, while the soil side of tamping point also has significant radial compaction; At the same level of dynamic compaction, heavy falling weight is suitable for deep soil and radial soil reinforcement, while light falling weight is suitable for rapid reinforcement of shallow soil. Conclusions The research results have a certain guiding significance for the selection of tamping methods of the same energy level dynamic compaction.

Construction activities are generating substantial amounts of construction waste due to the rapid increase in economic growth and infrastructure developments. A series of laboratory model tests were conducted to investigate the feasibility of using recycled aggregate as backfills to construct the rammed stone columns. Recycled aggregates and gravel aggregates with the same particle size distributions were used to construct the rammed stone columns. The direct shear test results showed that the recycled aggregate exhibits similar behavior of initial compression but more significant expansion compared to those of the gravel aggregate. The critical bearing capacity of the rammed stone column using recycled aggregate as backfills was 6.2%–6.5% lower than that using the gravel aggregate as backfill, but was 36.1% higher than that of the traditional stone column. The rammed stone column was failed in bulging failure mode with the maximum bulging position of approximately 2d from the column head. The critical bearing capacity of the rammed stone columns could be estimated according to that of the traditional stone column by considering the effects of the tamping energy. [ABSTRACT FROM AUTHOR]

In light of the significant presence of liquefiable sandy silt layers in the foundation of the airfield area at the Beijing Daxing airport, this study employed a low-energy, small spacing, and low blow count dynamic compaction method to treat it.To assess the compaction effects and determin the parameters of the compaction process, two energy levels of 1 000 kN·m and 2 000 kN·m were selected, with each energy level tested at 4, 6, 8, 10, and 12 blow counts. Additionally, the effect of the surface frozen soil layer on compaction was investigated using 1 000 kN·m energy level with 4, 6, and 8 blow counts. The full depth standard penetration, surface wave and dry density tests were carried out in the dynamic compaction test area. The experimental results revealed that the sandy silt soil foundation exhibited increased compaction, propagation wave velocity, and enhanced liquefaction resistance after dynamic compaction. Optimal blow counts were determined as 10 and 8 for energy levels of 1 000 kN·m and 2 000 kN·m, the corresponding dynamic consolidation depth is 4.5m and 5.5m, and the eliminating liquefaction depth is 4.3m and 5.3m, respectively. Besides, the standard penetration test requires a minimum of 10 and 12 blows in the depth range of 4.5 m and 5.5 m for energy levels of 1 000 kN·m and 2 000 kN·m. At the optimal blow counts, the dry density of the surface layer of the original foundation should not be less than 1.45 g/cm3. The experimental results suggest that, for foundation treatment in the runway area, the dynamic compaction level of 2 000 kN·m is suitable, and 1 000 kN·m dynamic compaction level is used for foundation treatment in the apron and taxiway area.

The objective of this research is to develop an improved uniaxial static compaction method to address the limitations of the traditional Proctor's dynamic approach for soil compaction. This new approach offers reduced labor, enhanced soil density, and increased compactness. The study compares of static soil compaction characteristics with various soil parameters and explores the concept of Equivalent Static Compaction Energy (ESCE). A diverse range of fine-grained soils with varying range of plasticity was investigated, and a significant correlation of compaction parameters attained by static compaction was observed with the corresponding value of static compaction energy, degree of saturation, void ratio, and plastic limit of soil. The research resulted in the creation of constant-energy curves for static compaction, which were compared to dynamic compaction curves from four compaction attempts. From the study, the ESCE corresponding to standard Proctor, reduced standard Proctor, and reduced modified Proctor tests were found to be within the range of 180-340, 155-308, and 532-664 KJ/m3, respectively. It was also observed for the static compaction method that after reaching the maximum level of compaction, the dry unit weight of the soil specimen remains constant with further increases in compaction energy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study presents a novel procedure and mathematical model employing four artificial intelligence AI algorithms to predict the cumulative degree of soil compaction CDSC during dynamic compaction DC. The four AI algorithms used in this study involve artificial neural network ANN, support vector regression SVR, gradient boosting machine GBM, and random forest RF. Input variables involve the average SPT N value Nini before dynamic compaction, cumulative applied energy normalized with a cross-sectional area of tamper Ea, and the number of the tamper drops Ndrops. Apart from cross-validation with a testing set, additional in situ test data gathered from a different section within the study site are used to assess the generalization capacity of the AI models. In addition, out-of-distribution analyses for the four AI algorithms are conducted in the context of parametric studies. The CDSC prediction performance for the four AI models leads to high prediction metrics of accuracy with the r2 greater than 0.9 for the testing scenario while the r2 of the other AI models is greater than 0.9 when out-of-sample data are considered except for the GBM. The ANN appears to be the best model as the parametric study takes into account out-of-distribution data and suggests a robust relationship between input variables and CDSC that is more coherent with engineering principles for DC. Finally, the ANN model is utilized to develop a new mathematical model for CDSC prediction. [ABSTRACT FROM AUTHOR]

To solve the problem where the prediction formula for vibration velocity by dynamic compaction cannot fully reflect the elevation amplification effect, the elevation amplification effect of vibration velocity by dynamic compaction was studied theoretically, and the factors that influence the elevation amplification effect of vibration velocity by dynamic compaction were systematically analyzed in this paper. The elevation amplification effect of a loess high slope under dynamic compaction is coformed by the refraction and reflection superposition effect of dynamic compaction vibration waves at the soil layer interface and the diffraction effect of dynamic compaction vibration waves. The propagation path of dynamic compaction vibration waves in soil was analyzed, and the elevation amplification effect was verified theoretically. The related physical quantities that affected the dynamic compaction vibration velocity of a loess high slope were analyzed based on the dimensional analysis method, and the calculation and improved calculation formulas that considered the elevation amplification effect of dynamic compaction vibration velocity were obtained. The multiple regression analysis of the calculation and improved calculation formula that considered the elevation amplification effect of the dynamic compaction vibration velocity was carried out using MATLAB with engineering examples. The results show that the relative error of the two formulas is small when the elevation difference is small; when the elevation difference is large, the calculation accuracy of the improved calculation formula that considered the elevation difference is higher, and it is more in line with the actual situation. Finally, according to the selected maximum allowable value of the slope particle velocity (e.g., 1.5, 2.0, and 2.5 cm/s), the allowable safe distance for dynamic compaction on a loess high slope is proposed area of northern Shaanxi Province, China. The results of this paper could provide a reliable basis for predicting vibration velocity by dynamic compaction in the Loess Plateau area of northern Shaanxi Province, China. They might have a reference value for dynamic compaction vibration control under similar terrain environments with large elevation differences and provide a safe guide for a dynamic compaction construction site in the Loess Plateau area of northern Shaanxi Province, China. [ABSTRACT FROM AUTHOR]

Dynamic Compaction (DC) is employed as a simple and economical method to improve weak soils in the last few decades. DC is usually applied for granular soils by falling a heavyweight (up to 40 tons) from a height (up to 40 m) at regularly spaced intervals. Significant issues in DC are the weight and height of the tamper, compaction pattern and the distance between tamping locations. Incorporated innovation in this paper is to introduce an analytical approach to optimize the compaction pattern and DC variables regarding regular constraints. The required energy for compaction is evaluated for square and diamond patterns. DC optimization is a non-linear and nonconvex problem due to nonlinear equations in soil compaction behavior. Thus, a metaheuristic approach (Genetic Algorithm) is employed to find global optimum. The optimum answer presents the minimum compaction energy in each pattern. Results indicated that the maximum allowed values of tamper mass and the number of tamper drops were required to minimize compaction energy. The ratio of compaction energy at diamond pattern to square one was also found to be about 0.75 to 0.90 for the same compaction conditions. [ABSTRACT FROM AUTHOR]

This paper focuses on the dynamic compaction experimental investigation of ADC12 alloy powder using laser impact, leveraging the high strain rate and controllable precision of pulsed lasers. The effects of varying laser energy (Em) and impactor thickness on the relative density, microstructure, and microhardness of the ADC12 alloy powder billets were examined. Utilizing 2D multi-particle finite element simulation (2D MPFEM), the densification mechanism of these billets was analysed with the help of coordination numbers. The simulation also provided insights into the particle velocity, equivalent plastic strain, and adiabatic temperature increase during compaction. Key findings include that a relative densification of up to 97.27% in the billets is achievable when the laser energy reaches 6J. Notably, a decrease in impactor thickness at constant laser energy leads to a more uniform microstructure and microhardness in the billet. Simulations with the 2D MPFEM demonstrate that thinner impactors allow billets to absorb more energy, thereby increasing particle velocity and plastic strain. This enhances both the relative density and mechanical properties of the billets. The simulation explores the stress distribution during compaction and captures the adiabatic temperature rise on the surface of the pressed billet that occurs in the transient, which is consistent with experimental revelations that heat softens or even locally melts the particles to produce sintering. This study offers new insights into the formation process of these billets from a microstructural standpoint, elucidating the relationship between processing conditions and the resulting material properties.

Estimating the densification efficiency of soil fillers is the main topic in dynamic compaction (DC). However, existing methods fail to assess the different contributions between tamper weight (M) and drop distance (H). In this study, a DC laboratory setup was developed to allow such different contributions to be analyzed. A series of DC tests were conducted on a red clay from China with six combinations of tamper weight and drop distance and twenty multiple blows in each combination. The soil responses including crater depth, plastic deformation, impact stress, and inside stress spectrum were recorded. It was observed that with the same tamping energy and momentum, a heavier tamper with a lower drop distance enabled a deeper crater depth and larger plastic deformation. Further examination showed that a heavier tamper caused impact stress with a longer period, increasing the stress wavelength and propagation ability. Therefore, a larger soil body was involved in the compaction process. Additionally, with the same value of MH0.3, different combinations of tamper weight and drop distance shared similar impact stress and soil responses, which is recommended as the new index to estimate the DC densification efficiency for the studied red clay. [ABSTRACT FROM AUTHOR]

Improved depth is of fundamental importance for earth-filled foundations with dynamic compaction (DC) and is closely relevant to the mechanical characteristics of earth fillers under impact load. This study carried out numerical DC tests on fine-grained soil to estimate the improved depth more easily and accurately. The filler's multiscale responses, including crater depth and porosity, were evaluated. Results showed that a heavier tamper weight with a lower drop distance was relatively more efficient in densifying soil fillers, although the tamping energy (MH1.0) and tamping momentum (MH0.5) were the same; however, contrary results were observed under the same value of MH0.2. In addition, three different combinations of M and H led to similar soil responses under the same value of MH0.3, which is thus recommended as the new index to estimate the improved depth and densification efficiency of DC. A mechanistic analysis found that M contributes more than H to compact soil fillers, which can be quantified by contribution ratio α. Moreover, large-scale field DC tests confirmed the findings. [ABSTRACT FROM AUTHOR]

The cast-in-place (CIP) pile is a type of deep foundation that has been widely used in various soils. However, the performance of CIP pile in dynamically compacted (DC) soil-rock mixtures has been rarely investigated. This study presents a field investigation on the performance of CIP piles in DC treated soil-rock mixtures. First, a 30-meter-thick soil-rock mixture layer on site was improved using DC (maximum energy level =10,000 kN·m) on grouting area and non-grouting area. Second, two groups of six CIP piles with a diameter of 1.2 m and a length of 34 m were constructed. After that, static pile load tests (SPLT) were carried out to evaluate the performance of CIP piles. The testing results suggest that the compressive bearing capacity of CIP pile in grouting area is identical to that installed in non-grouting area. The pile displacement in grouting area, however, was reduced over 40% under an applied load of 12,000 kN compared to non-grouting case. The DC treatment mobilized the shaft resistance in upper part of test piles (0 ∼ 10 m). The applied load shared by shaft resistance mobilized at depth of 0 ∼ 10 m is beyond 77% regardless of grouting, and the smaller the applied load, the higher the shared ratio. It indicated that the DC can significantly eliminate collapsibility within the main influence depth from water injection test. The grouting can eliminate the potential collapsibility and negative frictional resistance of pile side, which is especially beneficial in reducing pile displacement, improving the strength of thick soil-rock mixtures, and increasing bearing capacity of the CIP piles.

Dynamic compaction (DC) represents a cost-effective method for reinforcing subgrade and is particularly suited to treating large-scale building subgrade. Nevertheless, the effect of DC reinforcement on high groundwater level (HGL) subgrade remains uncertain due to the lack of clarity surrounding the energy transfer mechanism of DC in HGL subgrade. In this paper, an outdoor model test of HGL subgrade was conducted based on the DC method. The temporal evolution of the internal transverse and vertical dynamic stresses in soil under different water levels, energy levels, and tamper weight conditions was monitored, and the DC mechanism of HGL subgrade was described from the perspectives of the dynamic stress waveform, peak development, and attenuation. On this basis, a novel methodology for assessing the extent of subgrade reinforcement through the utilization of impulses was put forth, thereby facilitating a more precise evaluation. The results showed that the HGL is obstructive in DC energy transfer. The peak dynamic stress, depth of impact and maximum impulse per unit area were markedly diminished when tamping the water surface. The study results also recommend that construction could expand the application range of the DC method and provide engineering suggestions for the selection of construction parameters and subsequent building construction.

By combining the distinctive advantage of the pulsed laser with a high strain rate, this study conducts dynamic compaction experiments with high-strain rate laser shock and quasi-static compaction with a low strain rate on aluminum-based composite powder (Wp/Al) and analyzes the effects of pressing pressure and Wp content on the relative density, surface microstructure, demolding pressure, radial rebound, and mechanical properties of Al-based composite (Wp/Al) compacts under the two modes of action. The shock wave propagation process, densification process, and adiabatic temperature rise in the pressed billet at high strain rates due to laser shock are analyzed in combination with 2D MPFEM. Results show that the relative density of the billets decreases as the Wp particle content increases and that the relative density of the billets obtained with high-strain rate laser shock dynamic compaction is 97.62%, which is up to 2.9% higher than that of quasi-static compaction with low strain rate, the demolding pressure decreases by up to 1.56 times, and the hardness increases by up to 13.5%. The hard particles Wp are evenly distributed on the surface of the billet, and no significant aggregation of hard particles is observed. The 2D MPFEM reveals that the speed between particles within the powder at the beginning of the pressing reaches the minimum collision speed of welding, which is beneficial to the particles to achieve improved adhesion; laser high-speed impact under the particles due to inertial effects produces severe plastic deformation, which in turn improves the formability of the powder; in the process of laser shock the temperature at the edge of the particles is greater than the temperature inside the particles, and the temperature near the upper impactor is higher. In addition, the results of the simulation study are compared with the experiments and are found to be remarkably consistent. [ABSTRACT FROM AUTHOR]

Dynamic compaction is a common foundation treatment method for loess and it is significant to understand the mechanical behavior of loess after compaction for engineering construction in loess areas. To gain insight into the variation of mechanical properties and microscopic mechanisms of loess under different compaction conditions, a series of indoor tests including particle size analysis, oedometer test, unconfined compressive strength test and scanning electron microscope imaging were carried out using intact and compacted loess in the compaction field as test materials. The results show that the ameliorative effects of dynamic compaction on the compressibility, collapsibility, and compressive strength of loess decline with increasing soil depth. Furthermore, the mechanical behaviors of loess at the compaction point are more pronounced than that of the loess between compaction points. Although increasing the ramming energy can improve the reinforcement effect, it does not change the spatial variability of the engineering properties of compacted loess with depth, compaction point and inter- compaction location. During the compaction process, the directional distribution of pores is weakened and the morphological complexity is increased as the macropores within the loess change to mesopores and then to small pores and micropores. The sequence of evolution for the loess structure is overhead-mosaic-flocculent with an increase in compactness. In addition, the clay content and nonuniformity coefficient are all positively correlated with the mechanical properties. These discoveries help better cognition of the reinforcement process for Malan loess subjected to dynamic compaction, as well as the stability study of loess foundations. [ABSTRACT FROM AUTHOR]

In order to investigate the mechanism of slope foundation reinforcement under the dynamic effect of top slope compaction, model experiments and numerical simulations were carried out. In the experiments, the hammer weight and drop height were controlled. The deformation characteristics and dynamic response characteristics of the natural slope during the compaction process were tested in groups. The concept of the plastic zone formed by compaction was used to explain the acceleration change mechanism during compaction. The experimental results were further discussed combined with numerical simulations. The results show that the effective reinforcement area formed by the ramming impact is elliptical, the effective influence radius of compaction on soil vibration was less than three times the hammer diameter. The compaction displacement and acceleration value tended to stabilize after the first three compactions. Under the same compaction energy level, the influence of hammer weight on displacement at the ramming point is more significant than that of drop height, that is, “ heavy hammer and low drop distance” is better than “ light hammer and high drop distance”. Compaction on the slope top mainly affects the slope top safety, causing a significant increase in horizontal displacement at the slope top and middle, but has a smaller impact on the slope foot. The experimental results can provide a reference basis for the design of slope foundation reinforcement scheme and the control of construction technology. [ABSTRACT FROM AUTHOR]

Laser impact dynamic compaction experiments and 2D multi-particle finite element method (MPFEM) simulations were carried out on aluminum–copper (Al–Cu) binary-based composite powders. Al–Cu compacts with densities of about 95% were successfully prepared at the maximum laser energy of 1.8 J. Research trends indicate that higher power lasers could nearly achieve the theoretical densities. Analysis of the influence laws of laser energy and copper powder mass fraction on the densities of Al–Cu compacts was carried out, and the effects of microstructure and microhardness of Al–Cu compacts on their mechanical properties were investigated, as well as the stresses and velocities in the dynamic compaction process of Al–Cu composite powders were analyzed. The results showed that the relative densities of composite powder compacts of Al-5 wt%Cu gradually exceeded those of Al-10 wt%Cu and Al-15 wt%Cu with the increase of laser energy. In laser impact dynamic compaction the mechanism of inter-particle joining was solid-state press-welding, and the increase in the hardness of the Al–Cu compacts could be attributed to the inherent hardness of the hard particles. The upper particles have a localized maximum velocity of more than 300 m/s, which met the explosion welding velocity, thus localized cold welding occurred and contributed to the inter-particle connection.

Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests were performed to obtain the design parameters before official DC operation. The standard penetration test (SPT), shallow plate-load test (PLT), and deformation investigation were conducted in two improvement regions (A1 and A2) with varying tamping energies. During the deformation test, the depth of the tamping crater for the first two points’ tamping and the third full tamping was observed at two distinct sites. The allowable ground bearing capacity at two disparate field sites was at least 360 kPa. The reinforcement depths were 3.5 and 3.2 m in the A1 and A2 zones, respectively. The DC process was numerically analyzed by the two-dimensional particle flow code, PFC2D. It indicated that the reinforcement effect and effective reinforcement depth were consistent with the field data. The coral sand particles at the bottom of the crater were primarily broken down in the initial stage, and the particle-crushing zone gradually developed toward both sides of the crater. The force chain developed similarly at the three tamping energies (800, 1500, and 2000 kJ), and the impact stress wave propagated along the sand particles primarily in the vertical direction.

The dynamic compaction mechanism of high-groundwater-level (HGL) foundations is still unclear, which seriously affects the engineering application of dynamic compaction in the riverbed and land reclamation. In this study, a dynamic compaction model test was established to analyze the vibration acceleration of the tamper, the soil surface, and the soil interior under different depths of groundwater level. Meanwhile, the propagation of the vibration wave was also analyzed, and the energy dissipation of dynamic compaction under the HGL foundation was studied combined with the modal damping ratio (ζ). The results showed that HGL resulted in poor foundation improvement. The main effects were the energy consumption and the friction reduction between the particles when the tamper was in contact with the water, which resulted in vibration acceleration and a sharp decrease in crater depth. The crater will not maintain its cylindrical shape, and further tamping will negatively affect the reinforcement. Vibration analysis showed that dynamic compaction results in dense soil with an increased damping ratio, but when the soil is tamped at the HGL foundation, the soil tends to oscillate, and the damping ratio decreases. In terms of energy, more than 70% of energy was dissipated directly under the tamping point of the high-groundwater-level foundation. Dynamic compaction has been extended from land foundation reinforcement to artificial reclamation foundation as an economical and environmentally friendly foundation treatment technique. The groundwater level in the coastal area is usually higher than that on land, which plays a decisive role in the success of dynamic compaction. However, there are few theoretical and experimental studies on the dynamic compaction of high-groundwater-level foundations. This paper analyzed the energy transfer and consumption of the dynamic compaction method for high-groundwater-level foundations from the perspective of vibration waves. The results showed that compared with dry sand, dynamic compaction of high-groundwater-level foundations will obviously consume reinforcement energy. Dynamic compaction causes groundwater levels to rise around the tamping point. The higher the tamping energy level, the more obvious the groundwater level rise. The results can provide a reference for expanding the treatment range of the dynamic compaction method and applying the dynamic compaction method to high groundwater foundations. [ABSTRACT FROM AUTHOR]

Featured Application: The study provides effective guidance for designing isolation trenches in similar dynamic compaction processes, emphasizing the importance of considering spatial attenuation characteristics and selecting appropriate trench depths and locations. Dynamic compaction is a widely used method to strengthen the foundation, which can cause significant impacts on surrounding structures, making vibration control measures necessary. This study investigates the effectiveness of isolation trenches in reducing ground vibration caused by dynamic compaction in a typical multi-layered alluvial soil foundation adjacent to the Yangtze River. A combination of field testing and numerical simulation was employed to evaluate the vibration isolation effect of trenches at different depths and locations. The results show that trenches have a significant vibration isolation effect on the side away from the tamping point, but they can have an amplifying effect between the trench and tamping point. The effectiveness of the isolation trenches increases with deeper trenches and distance from the tamping point, but the amplification effect decreases with increasing depth. Therefore, when employing trenches, reinforcement measures must be adopted, and a suitable trench depth should be selected. The closer the isolation trench to the dike, the better the protection will be. The study provides effective guidance for designing isolation trenches in similar dynamic compaction processes, emphasizing the importance of considering spatial attenuation characteristics and selecting appropriate trench depths and locations. [ABSTRACT FROM AUTHOR]

A three-dimensional finite element numerical model is proposed to study the dynamic behavior of foundations placed on densified soils. The densification of soil was done by dynamic compacting. The characteristics of densified soil are organized in four soil classes according to Eurocode 8(NF EN 1998). The mechanical parameters of the densified soil are used to determine the dynamic response of the foundations before and after the densification process. The formulation is based on the sub-structure method, the characteristic of the soil and the foundations are considered viscoelastic. Dynamic excitations are applied to the center of the foundation; the displacement response is obtained by applying a vertical and a horizontal load to the centers of the foundations. The obtained results are presented in terms of vertical and horizontal displacement amplitude for all categories of densified soil.

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Engineered fills, such as roads, earthen dams, embankments, and earthen sites, are enhanced by compaction to increase strength and decrease compressibility. Static and dynamic compaction are the most popular and important methods in geotechnical engineering practice with different compaction mechanisms. However, the significant differences in the physical and mechanical properties between both compaction methods that have been reported in the literature were limited to clay or sand. Limited attempts have been made to quantify the variations in silt's mechanical attributes that were caused by the sample preparation method. A series of consolidated drained triaxial shear tests and some mercury intrusion porosimetry (MIP) tests were constructed to interpret this. The results showed that static and dynamic compaction had a significant influence on the mechanical properties of the silt coupled with the molding water content. The shear strength of the dynamically compacted samples was higher than those of the statically compacted samples, as was cohesion (c), and the sample preparation method had little effect on the internal friction angle (φ). Furthermore, samples that were compacted at optimum water content (wot) had greater strength than those compacted on the dry or wet side of the optimum. Compared with the static compaction sample, the pore size distribution curve of the dynamic compaction sample shifted to the left with the peak pore size, distribution density, and the interaggregate pores proportion decreased. The strength discrepancy could be traced to differences in the silt structure features, for example, pore size distribution and particle orientation between statically or dynamically compacted specimens. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, a dynamic compaction soil box test is performed to analyze the effect of changes in energy according to the pounder tamping number of dynamic compactions on ground improvement. As reproducing the test on the in situ ground is challenging, a 3.0 m × 2.4 m × 1.0 m soil box is used. The number of pounder tamping repetitions of the dynamic compaction is tested in up to six steps, five times at each tamping point. The change in excess pore water pressure appears to begin to converge at step three (Nd = 15) of pounder tamping. The change in pore water pressure with respect to the number of tamping using the finite element analysis program AFIMEX GT-2D is found to have an effect at up to 4.0 m vertically and 3.0 m horizontally, similar to the results of the soil box test. The static cone penetration resistance at each pounder tamping stage increases by 1.3, 1.7, and 1.1 times at step two (Nd = 10), step three (Nd = 15), and step six (Nd = 30) of tamping, respectively. The depth of improvement coefficient (α) ranges from 0.26 to 0.52, with an average of 0.39. The improvement effect of the in situ improved ground can be inferred in advance from the correlation between the number of pounder tamping repetitions, ΔN, and the internal friction angle. Once the ground improvement range is determined, it can be used to determine the in situ dynamic compaction energy (weight of pounder, tamping of height) using the given improvement depth coefficient (α). [ABSTRACT FROM AUTHOR]

High-filled red soil typically lacks sufficient bearing capacity, which can pose significant challenges when constructing building foundations. One economical and effective method for the reinforcement of high-filled red soil is the dynamic compaction (DC) method. However, the design parameters for reinforcing high-filled red soil using the DC method are largely based on experience, which indicates the significant value of field results of related engineering practice. In this paper, we report a field study that was carried out to investigate the effect of impact energy on the treatment of super-high-filled ground with red soil in southwestern Yunnan, China, where three pilot DC tests were designed and conducted with three different impact energies (4000 kN·m, 8000 kN·m and 15,000 kN·m). To evaluate the reinforcement effect and optimize the DC operational parameters, a series of in situ tests, including settlement monitoring, standard penetration tests, dynamic penetration tests, surface wave velocity tests and plate-load tests, were carried out. Furthermore, the improvement depth of DC was discussed. The results of the field study show that the characteristic value of the ground bearing capacity of the three test zones could reach 250 kPa, which coincides with the design requirement, although the improvement depth of testing zone III fails to reach the required depth. This study helps to improve the in situ recycling of high-filled soil, thereby promoting the sustainable development of engineering construction. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of dynamic compaction (DC) on ground improvement in foundation with a high groundwater table, based on a dynamic fluid–solid coupled finite element method with a cap model. Firstly, an analysis of dry ground was carried out to evaluate the effective improvement range, with the proposal of a normalized formula capturing the improvement effect. Then, the parametric studies include the effect of groundwater table, the permeability coefficient, drop energy, and soil type have been carried out to not only find that the groundwater table has a dominant influence on soil improvement by DC but also clarify densification mechanisms of ground improvement by DC on the soil nearby groundwater table, which is through analyzing the contours of effective mean stress. Finally, a relative enhancement index, RD, based on a total of 52 calculations is derived to evaluate the depth of improvement below the groundwater table for different scenarios. These relationships provide a valuable reference for the evaluation of ground improvement by DC for a foundation with high groundwater table and the applicability of the proposed procedure is illustrated by comparing its prediction with three cases of DC in the field. [ABSTRACT FROM AUTHOR]

Dynamic compaction (DC) is a ground treatment method that achieves soil densification effects using impact forces. The ground displacement of a crater induced by a hammer is often used for the determination of densification, but less attention has been paid to internal displacement in the ground. To establish an overall understanding of the displacements caused by DC, a laboratory experiment was conducted with sand. The experiment included four energy levels by changing the falling height of the hammer. Meanwhile, a calculation model based on stochastic media theory was proposed to calculate the displacement in the soil. The relationship between the geometric characteristics of the crater and the internal displacement of the soil was established in the model based on the experimental results. The ranges of the relevant parameters were determined, and the feasibility of the calculation model was verified. The model showed good consistency with the experimental data. By selecting the critical settlement, the model could be used to estimate the specific densification scope, including the reinforcement depth and radius. This method can provide a reference for the calculation and optimization of DC. [ABSTRACT FROM AUTHOR]

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Ground improvement was required for construction of the Jaber Al Ahmed New City located about 25 km west of Kuwait City, Kuwait. Loose to medium poorly graded sands and silty sands extended from ground level to a depth ranging from 5m to 9m. Dynamic compaction was employed, as an economic method, to increase the soil bearing capacity and reduce its compressibility for foundation design and construction. The testing program included borings and sampling, Standard Penetration Tests, Cone Penetration Tests, and Pressuremeter Tests before and after dynamic compaction. The area covered in this study is about 31415m² . The results indicated significant ground improvement and satisfaction of the specified acceptance criteria resulting in an allowable soil pressure for shallow foundation design, equal to or exceeding 300 kN/m². [ABSTRACT FROM AUTHOR]

This paper aims to propose a generalizable parameter calibration framework for discrete element method (DEM) and to develop the refined dynamic compaction DEM (RDCD) model for red-bed soft rocks (RBSR), which is used to investigate the contribution of tamping weight (W) and drop distance (H) to dynamic compaction quality control. Firstly, the linear model (LM) and the linear parallel bond model (LPBM) were selected to accurately represent the dynamic behavior of RBSR based on dynamic compaction characteristics. A generalizable calibration framework for LM and LPBM contact models was further proposed. Secondly, based on the calibration framework, a series of DEM simulations, parameters significance analysis, and physical tests were conducted to accurately calibrate the contact parameters of RBSR. Finally, the RDCD model for RBSR was developed, which was used to investigate the contribution of W and H to dynamic compaction quality control from a micro perspective. All results indicated that the proposed generalizable calibration framework could provide an accurate determination of RBSR contact parameters for dynamic compaction simulation. Specially, the lightweight inversion model for LPBM parameters was developed, enabling the rapid acquisition of contact parameters for RBSR. The LM parameters of RBSR were determined directly and indirectly, which could be directly applied to various RBSR. Moreover, the shockwaves generated by a heavier tamper with a lower drop distance had longer durations and larger propagation, enhancing the compactness of the overall specimen and generating larger and more uniformly distributed strong force chains. The dynamic compaction simulation results indicated that increasing the W could enhance dynamic compaction quality control. This paper contributes to the theoretical refinement of the contribution of W and H on-site dynamic compaction quality control. • A generalizable parameter calibration framework for discrete element method. • The refined dynamic compaction DEM model for red-bed soft rocks is developed. • The contribution of W and drop distance H to dynamic compaction is investigated. • The shockwaves generated by a heavier W have longer durations and propagation. [ABSTRACT FROM AUTHOR]

The studies of foundation treatment methods are carried out for the special and complex foundation in the fill, saturated silty fine sand and silt in the coastal backfill area of the coastal zone of the Shandong Peninsula. Based on the economical and efficient dynamic compaction method, the concept of integrated combined drainage is put forward. The relay drainage system of the shallow and deep vertical drainage channels and their relay horizontal drainage channels are designed, and field tests are undertaken. The monitoring data show that under the dynamic compaction load, the relay drainage system can coordinate drainage as a whole, which can quickly discharge the groundwater to dissipate the excess pore water pressure. The rise of groundwater level and dissipation of pore water pressure caused by dynamic compaction can be basically eliminated in about 7 hours. With continuous precipitation, the surface settlement is 0.7%～2.0% of the thickness of the upper soil mass. Under the dynamic load of dynamic compaction, the surface soil is compressed to 8.7%～10.9% of the thickness of the upper soil. The soil settlement is about 5 ‰ and 3 ‰ of the soil thickness at the buried depth of 3～7 m, and 2 ‰ of the soil thickness is at the buried depth of 7～10 m. The test data show that in the effective depth of dynamic compaction, the effect of foundation treatment is obvious, the engineering properties and the degree of consolidation of foundation are improved. The surface bearing capacity and deformation modulus meet the design requirements, the average bearing capacity of silt below 4 m is slightly lower than the design requirements, and the average degree of consolidation of mucky soil is 77%. The monitoring data of one month after tamping shows that the surface subsidence is within 25 mm, which tends to be stable, the layered settlement and pore water pressure are stable and slightly decreased.