Gravel Pile Composite Foundation Research Articles

Research on the Geosynthetic-Encased Gravel Pile Composite Highway Foundation in Low-Temperature Stable Permafrost Regions

In low-temperature stable permafrost regions, both active and passive cooling measures are commonly employed to ensure the long-term stability of highway structures. However, despite adopting these measures, various types of structural issues caused by permafrost degradation remain prevalent in high-grade highways. This indicates that in addition to preventing permafrost melting, structural reinforcement of the foundation is still necessary. Based on the analysis of the long-term foundation temperature field and settlement using the finite element method, which was validated through an indoor top-down freeze–thaw cycle test, this paper explores, for the first time, the feasibility of applying geosynthetic-encased gravel pile composite highway foundations—previously commonly used for permafrost destruction—in low-temperature stable permafrost areas where permafrost protection is the primary principle. By analyzing the long-term temperature field, settlement behavior, and pile–soil stress ratios of permafrost foundations influenced by both the highway structure and composite foundation, it was found that when the pile diameter is 0.5 m, pile spacing is 2 m, and pile length is 11 m, the mean monthly ground temperature of the permafrost foundation will not be significantly affected. Therefore, the properly designed geosynthetic-encased gravel pile composite highway foundation can be adopted in low-temperature stable permafrost regions where permafrost protection, rather than destruction, is required.

Physical model test study on strength characteristics of gravel pile composite foundation

In gravel pile composite foundation stability design, the shear strength of composite foundation is critically important. However, due to the size limitation of test equipment, it is difficult to obtain its shear strength in field. This study designs a laboratory shear model test to obtain the shear strength of gravel pile composite foundation, where a total of four group tests were carried out, including two nature soils and two gravel pile area replacement ratios. The shear strength parameters obtained by the shear model tests are compared with the results of empirical formula methods such as the Chinese Standard Method and Priebe Method to verify the accuracy of these two methods. It is demonstrated that for the Chinese Standard Method, the empirical formula's results are smaller than the shear model test results when the pile-soil stress ratio b is 1. When the pile-soil stress ratio b is 1.5, the results are close to each other. For the Priebe Method, the empirical formula results are all larger than the shear model test results, and it is especially unsuitable for the mud soil.

Three-Dimensional Discrete Element Analysis of Bearing Characteristics of Concrete–Cored Sand–Gravel Pile Composite Foundation under Cyclic Dynamic Load

Concrete-cored sand–gravel piles are a kind of composite pile formed by wrapping a concrete-cored pile with a sand–gravel shell, which has the advantages of both a rigid pile and bulk-material pile. The bearing characteristics of the concrete-cored sand–gravel pile composite foundation were investigated by establishing a three-dimensional discrete element numerical model for a cyclic dynamic loading test. The results show that the vertical stress of the core pile body fluctuates greatly at the beginning of loading, and the fluctuation amplitude decreases with the depth, and gradually tends to be stable in the middle and late stages, and the vertical-stress distribution is relatively uniform. The radial stress in the upper part of the core pile body fluctuates greatly, the fluctuation in the lower part is small, and the radial stress in each part of the core pile body gradually tends to be stable in the late-loading period. The radial stress factor of the core pile body reaches the stable speed with the foundation depth decreasing; the fluctuation amplitude of the pile-soil stress ratio decreases with the foundation depth and gradually tends to be stable with the increase in loading. The results of this study can provide a reference for the design and construction of a core sand pile composite foundation.

Bearing Capacity Characteristics of Compacted Cement Stabilized Gravel Pile Composite Foundation

Bearing Capacity Characteristics of Compacted Cement Stabilized Gravel Pile Composite Foundation

Temperature analysis of CFG pile composite foundation in high latitudes and low altitude island permafrost

PurposeCement fly ash gravel (CFG) pile composite foundation is an effective and economic foundation treatment approach, which is significant to build foundation, subgrade construction, and so forth. The purpose of this paper is to present a research on the temperature behaviours of high-latitude and low-altitude island permafrost under CFG pile composite foundation treatment.Design/methodology/approachIn the process of CFG pile construction, the temperature of permafrost and pile body was monitored using the temperature sensors. The influence of subgrade height and atmospheric temperature cycle on permafrost temperature was analysed by finite element simulation.FindingsIn the process of CFG pile construction, the change curve of pile temperature and the temperature of permafrost beside pile following time can be divided into six stages, and the duration of these stages is at least one month. The temperature variation of permafrost while constructing subgrade in FEM has a good agreement with the results of field temperature monitoring. The height of subgrade not only affects the maximum temperature increase of permafrost and the re-frozen time of permafrost after the construction of CFG pile composite foundation, but also affects the temperature variation amplitude of permafrost during atmospheric temperature cycle.Originality/valueThe research will provide a reference for the design on the CFG pile composite foundation used for island permafrost and guarantee the stability of the structure; thus, it has an important significance.

TEMPERATURE ANALYSIS OF HIGH LATITUDES AND LOW ALTITUDE ISLAND PERMAFROST DURING THE CONSTRUCTION OF CFG PILE

Cement fly ash gravel (CFG) pile composite foundation is an effective and economicfoundation treatment approach, which is significant to building a foundation, subgrade construction,and so forth. The present paper aims to investigate the temperature behaviours of high latitudesand low altitude island permafrost when the CFG pile was constructed, in which FEM and fieldtemperature monitoring of permafrost was utilized. The proposed findings demonstrate that thetemperature disturbance of permafrost is obvious when the CFG pile was constructed, and thetemperature variation of CFG pile and permafrost in FEM has a good agreement with the results offield temperature monitoring. Additionally, the influence of different height subgrade on thetemperature field of CFG pile composite foundation was analyzed by FEM. The proposed findingsdemonstrate that the height of subgrade affects the maximum temperature increase of permafrostand the re-frozen time of permafrost after the construction of CFG pile composite foundation.

Finite element analysis of gravel pile composite foundation under flexible foundation of Airport Engineering

On the basis of consulting data, the bearing mechanism of gravel pile composite foundation is analyzed in this paper. The use of ANSYS software under flexible foundation according to the plum blossoms gravel pile additional stress between pile and soil additional stress distribution, load on pile top stress and pile bearing rate of modulus ratio between pile and soil on the pile top stress and rate of pile bearing capacity, pile-soil effect the stress ratio was calculated and analyzed, providing reasonable design reference for the design of gravel pile composite foundation.

Settlement Analysis of Saturated Tailings Dam Treated by CFG Pile Composite Foundation

Cement fly ash gravel (CFG) pile composite foundation is an effective and economic foundation treatment approach, which is significant to building foundation, subgrade construction, and so forth. The present paper aims at investigating the settlement behaviors of saturated tailings dam soft ground under CFG pile composite foundation treatment, in which FEM and laboratory model test were utilized. The proposed findings demonstrate that CFG pile treatment is effective in reinforcing saturated tailings dam and loading has little influence on settlement of soil between piles. The variation of soil between piles settlement in FEM has a good agreement with the laboratory model test. Additionally, the cushion deformation modulus has a small effect on the composite foundation settlement, although the cushion thickness will generate certain influence on the settlement distribution of the composite foundation.

The Settlement Analysis of the Cement Fly-Ash Gravel Pile Composite Foundation of Baotou

This paper analyzes the causes of larger differences of final settlement calculated value of cement fly-ash gravel pile (CFG pile) composite foundation of Baotou with actual observed result of it. On the basis of analysis on a number of practical engineering data of Baotou, we modify the settlement formula of the CFG pile composite foundation and gain the modified coefficient applied to the settlement calculation of the CFG pile composite foundation of Baotou. The modified formula and coefficient proposed in this paper have a positive effect on the accurate settlement calculation of puting forward a more accurate correction formula and coefficient of the calculation of the CFG pile composite foundation of Baotou.

The Unified Solution of Gravel Pile Limit Bearing Capacity of Single Pile Composite Foundation

Based on the compaction effect of the gravel pile, the thick-walled tube model is established. Considering the gravel pile and pile materials with different properties of tension and compression of soil pile in the process of expansion, the influence of intermediate principal stress to improving the bearing capacity of foundation in the process of expansion, we use the planar axisymmetric double shear unified strength theory and present a gravel pile ultimate bearing capacity of single pile composite foundation unified expression. The theory study of gravel pile composite foundation and engineering practice has a certain guiding significance.

The Numerical Analysis of Gravel Pile Reinforcing Liquefiable Silt

A three-dimensional numerical simulation about gravel pile reinforcing liquefiable silt foundation was built, and the influence of gravel pile on the liquefiable silt anti-liquefaction was discussed. Results show that under seismic load, gravel pile has obvious cushioning effect, and compared with natural foundation, the maximum horizontal vibration acceleration of the gravel pile composite foundation surface layer is obviously decreased; drainage effect of gravel pile is very significant and the larger is the gravel pile permeability coefficient, the better is the drainage effect; as earthquake intensity largens, silt liquefaction scope increases; of both natural foundation and composite foundation, the pore pressure ratio variation with depth is that the middle is bigger than the top and bottom, and middle layers are more likely to be liquefied; the greater is the seismic acceleration, the larger is the shear stress.

The Application of the Ground Penetrating Radar in the Inspection of Gravel Pile Composite Foundation

The ground penetrating radar can be used in the inspection of the gravel pile composite foundation, and we can make a qualitative analysis of the gravel pile integrity. The technique has the advantages of rapid, accurate and real-time processing and display especially available to collect continuously high-resolution sections of underground pile. The results showed that GPR technology will provide amount of detailed and reliable information to the engineering quality inspection of composite foundation.

Experimental Study on Pile and Soil Stress of Cement Fly-Ash Gravel Pile Composite Foundation During the Process of Filling Embankment

Experimental Study on Pile and Soil Stress of Cement Fly-Ash Gravel Pile Composite Foundation During the Process of Filling Embankment

Characteristics of Liquefaction Resistance for the Saturated Silty Soil Ground Treated by Compacted Gravel Pile Composite Foundation

Based on Beijing-Shanghai high speed railway, the numerical simulation mainly researched on the seismic behavior for the saturated silty soil ground, which was treated by compacted gravel pile composite foundation. It has been analyzed that the region of liquefaction distribution and the transferring rule of excess pore water pressure under a series of input acceleration seismic loads in the treated and untreated foundation. The research results indicate that the untreated saturated silty soil ground is almost whole liquefaction when the amplitude of input acceleration is more than 0.15 g. While for compacted gravel pile composite foundation, out of treated region is less liquefaction when the amplitude of input acceleration is 0.15 g, with the increasing of input acceleration, liquefaction region is further more and gradually expands to the inner soil between piles, and compacted gravel pile composite foundation is only partial liquefaction when the amplitude of input acceleration is 0.25g. Excess pore water pressure is increased with the increasing of input acceleration seismic load, and the increasing of excess pore water pressure can be restrained effectively by compacted gravel pile composite foundation, and the quality of liquefaction resistance is improved. The design of compacted gravel pile composite foundation can satisfy the seismic requirements of Beijing-Shanghai high speed railway under the condition of 7 degree seismic fortification.

Characteristics of Liquefaction Resistance for the Saturated Silty Soil Ground Treated by Compacted Gravel Pile Composite Foundation

Characteristics of Liquefaction Resistance for the Saturated Silty Soil Ground Treated by Compacted Gravel Pile Composite Foundation

Working mechanism of two-direction reinforced composite foundation

Based on the discussion about working mechanism of horizontal reinforcement and that of vertical reinforcement, respectively, the working mechanism of two-direction reinforced composite foundation was studied. The enhancing effect of horizontal reinforcement on vertical reinforced composite foundation was analyzed. A simplified calculation method for such two-direction reinforced working system was presented. A model experiment was carried out to validate the proposed method. In the experiment, geocell reinforcement worked as the horizontal reinforcement, while gravel pile composite foundation worked as the vertical reinforcement. The results show that the calculated curve is close to the measured one. The installation of geosynthetic reinforcement can increase the bearing capacity of composite foundation by nearly 68% at normal foundation settlement, which suggests that the enhancing effect by geosynthetic reinforcement should be taken into account in current design/analysis methods.