CFG Pile Composite Foundation Research Articles

Mechanical behavior analysis and bearing capacity calculation of CFG pile composite foundation on coral sand site

Coral sand foundation formed by hydraulic fill often faces the problem of poor bearing capacity. This paper proposed for the first time to apply CFG pile composite foundation to coral sand sites to verify the feasibility of this scheme and understand its mechanical characteristics. Firstly, taking on-site coral sand as the research object, a pile sand interface shear test was conducted to clarify the mechanism of pile side friction. At the same time, the ultimate bearing capacity of CFG pile and its composite foundation was measured through in-situ static load tests. Then, based on the strength parameters of the pile sand interface revealed by indoor tests, numerical simulations were conducted to analyze the bearing characteristics of CFG piles and their composite foundations. Finally, a method for calculating the vertical bearing capacity of rigid piles in composite foundation considering interface parameters was proposed. The results showed that the bearing capacity characteristic values of single pile and composite foundation meet the design requirements; The interface friction angle and cohesion together increased the ultimate side friction by 64.41%; The load is mainly borne by the pile tip resistance, and the increase of the interface friction angle will make the proportion of the side friction load first increase and then decrease more obviously; The pile soil stress ratio first increased and then tended to stabilize as the interface strength increased. Compared with the field static load test results, the rationality of the calculation method for composite foundation rigid piles was verified. This study may have reference significance for the design and construction of coral sand foundation treatment in offshore island and reef projects.

Study on the Impact of Foundation Pit Precipitation on Neighboring CFG Pile Composite Foundation

The numerical simulation was used to examine the impacts of pit precipitation and the presence or absence of waterproof curtain on the CFG pile composite foundation near to the under-construction pit, and the following primary results were reached. For starters, the precipitation will force the CFG pile composite foundation to slope towards the entire under-construction pit. Second, the waterproof curtain can help to mitigate the negative impact of pit precipitation on the nearby CFG pile composite foundation.

Research on Application of CFG Pile Composite Foundation Bearing Capacity Detection Technology

Research on Application of CFG Pile Composite Foundation Bearing Capacity Detection Technology

Experimental study on load sharing characteristics of long-short CFG pile composite foundation adjacent to rigid retaining wall rotating about its base

Practicing geoengineers and researchers generally consider the load sharing behavior in multi-type pile composite foundation as an important design aspect. On the other hand, due to urbanization, such foundation system in cities will inevitably appear next to supported excavation. This paper discusses the result from relatively large-scale indoor experiment conducted to investigate the load sharing behavior of loaded long-short CFG pile composite foundation behind a neighboring rigid retaining wall undergoing rotation around the bottom. It was found that with progression of wall movement, the hidden load from soil displacement was borne by the piles with marked reduction in soil load sharing. At the end of wall rotation, the percentage of long piles’ head load increment needed to arrive at a new static equilibrium was about 12.57~32.22% while the end bearing increased by more than 97%. The consequences on the short piles, however, were manifested with an increasing pile head (13.42%) and toe (28.9%) load for the pile far from the wall whereas the closest one experienced a certain increment up to 15×10-4rad wall rotation and finally the head load and end bearing decreased to 8.28% and 12.63%, respectively. The 3D numerical back analysis conducted using FE software ABAQUS yielded the pile – soil stress ratio lower than the value obtained from the experiment but provided great insight into pile settlement characteristics during wall rotation.

Experimental Study and Measures on Engineering Characteristics of Diatomite Subgrade in Shengzhou

This paper takes the newly built railway passing through the diatom land area of Shengzhou and Xinchang in Zhejiang Province as an example. And based on the field test of soil samples, this paper pointed out that due to low natural density, large void ratio, high water content, dry shrinkage and wet expansion, relative deformation and strength, The diatomite are not suitable to be directly used as building foundation. Based on the static load of single pile, bearing capacity of composite foundation and in-situ vibration test of foundation bed, it proposed that CFG pile, plain concrete pile and reinforced concrete pile are suitable for diatomite foundation reinforcement. While screw pile has insufficient bearing capacity, due to soil compaction effect and poor pile forming effect of high pressure jet grouting pile. CFG and plain concrete pile composite foundation can meet the requirements of diatomite subgrade deformation, and plain concrete pile is much better. The raft structure has better integrity. The capillary waterproof and drainage board can significantly improve the waterproof and drainage effect, and reduce the adverse effect of dynamic load on diatom soil foundation. Based on the slope rainfall test, it is proposed that diatomite natural slope is easy to form network cracks and induce shallow landslide under the action of dry wet cycle. In addition, the effect of gentle slope and skeleton on Diatomite slope is better.

Dynamic response of CFG and cement-soil pile composite foundation in the operation stage

More and more attention is paid to the stability, safety and comfort of trains during its operation stage. When the train is running, in addition to the track gravity, it is also affected by the train load and earthquake, these dynamic effects will have a certain impact on the normal operation of the railway. However, the current research on the dynamic response of composite CFG and cement-soil compaction piles foundations under dynamic loads is rarely involved. Taking the composite foundation of Baoji-Lanzhou Passenger Dedicated Line as the research object, the dynamic response of the composite foundation under train load, seismic wave and train-seismic load is analyzed in detail by using numerical simulation software. The results show that under the train load, the maximum displacement occurs at the action position of the train load, and it is gradually reduced downward. The overall displacement is not large, and the influence on the operation of the train is little. Under earthquake action, the displacement is the largest at the bottom of subgrade, and gradually decreases upward, which has little effect on the top of embankment. Under the train-earthquake action, the displacement of subgrade bottom and embankment top is larger, and gradually decreases to the middle. It provides the corresponding theoretical basis for the same type of railway subgrade engineering.

Study on the role of cushion of composite ground and the choice of its depth

Cushion design on CFG pile composite foundation is an important part of CFG pile. Through theoretical analysis, the mechanism of cushion improving composite foundation is obtained, and the relationship curve of cushion thickness, modulus, pile-soil stress ratio, length of negative friction zone and settlement is analyzed, so as to provide basis for cushion thickness design of CFG pile composite foundation.

The Application of CFG Pile Composite Foundation in the Reconstruction of the Dujiangyan

There are many shallow treatment methods for soft foundation, CFG pile composite foundation is one of the common treatment methods. In this paper, the application of CFG pile in multi-storey residential building is introduced, it is pointed out that CFG pile composite foundation is a simple, rapid, economical and effective foundation treatment method.

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.

CFG桩复合地基现场检测与模拟分析研究

CFG桩复合地基现场检测与模拟分析研究

Numerical Analysis of the Settlement of CFG Pile Composite Foundation Subgrade During Construction in High Speed Railway

According to the typical geological conditions of Wuhan Guangzhou passenger dedicated line reinforced section by CFG pile, the FLAC3D finite difference program is used to simulate the settlement deformation characteristics of subgrade filling process. The settlement deformation is also calculated by theoretical method. By comparing the calculated results with the numerical simulation results the feasibility of the model is verified. Results show that: The uneven settlement as basin appears on the subgrade surface top. The maximum settlement is at subgrade centerline. It gradually decreases towards the slope. The settlement at shoulder is the smallest.

Optimization Design on CFG-Pile Foundation with Different Cushion Thickness in Beijing-Shanghai High-Speed Railway

The cushion, as the core technique of CFG pile composite foundation, greatly affects the foundation characteristics of carrying abilities and deformation. A three-dimensional simulation model of CFG multi-pile composite foundation is established via MIDAS/GTS finite element software to investigate the influence of different cushion thicknesses on the deformation and stress characteristics in CFG pile composite foundation. The design of the Beijing-Shanghai high-speed railway is optimized in accordance with the post-construction settlement of subgrade and the utilization requirements of pile caps and soil between piles. The results show that the settlement in composite foundation would be even applying pile caps and that the optimized thickness of cushion is 0.4 m below the piles which also could satisfy the requirements of the Railway Codes.

The Characteristics and Construction of CFG Pile Composite Foundation

This paper expounded the engineering characteristics and construction technology of CFG pile composite foundation, introduced the construction process of CFG pile and main points for attention, and proved that CFG pile treatment scheme is practical and feasible combined with the engineering practice.

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.

Experimental Study of Dynamic Characteristics on Composite Foundation with CFG Long Pile and Rammed Cement-Soil Short Pile

Based on the idea of optimization design of pile type, the two kinds of the typical pile type are selected, which containing flexibility pile (e.g. rammed cement-soil pile is for short RCSP), and rigid pile (e.g. cement-flyash-gravel pile is for short CFGP). The three kinds of the composite foundation are designed, which are CFGP, CFG long pile and CFG short pile (for short CFGLP-CFGSP), CFG long-short pile and rammed cement-soil short pile (for short CFGLP-RCSSP). Natural earthquake is simulated by using the engineering blasting; the dynamic characteristics and dynamic response of the composite foundation are studied through field test. CFGLP-RCSSP is closed to linear relation. The bearing capacity of the four composite foundation of the CFGP, CFGLP-CFGSP, and CFGLP-RCSSP in the site are 225 kPa, 179 kPa, and 197 kPa, separately increases 150%, 98.8% and 119% compared to the natural foundation. The vibration main frequency is mainly depended on properties of foundation soil and piles between vibration source and measuring point, pilling load value. Horizontal vibration main frequency greater than the vertical vibration main frequency and the vertical vibration main frequency close to the first-order natural frequency of composite foundation. With the pilling load increasing, the CFGLP-RCSSP pile composite foundation combined frequency decreased. Under the same blast energy, the acceleration peak on the CFG pile composite foundation is less than CFGLP-CFGSP the corresponding values, as the load increases, the peak acceleration gently. CFG pile composite foundation is favorable on seismic. The distribution of peak acceleration is consistent within 4 m from pile top in the CFGLP_RCSSP composite foundation. The maximum of the horizontal acceleration peak along the pile body occurs at a distance of pile top 4 m or the pile top, and that of vertical acceleration peak occurred at a pile top.

A Prediction Method of Bearing Capacity of CFG Pile Composite Foundation Based on Support Vector Machine

A prediction method of bearing capacity of CFG pile composite foundation was presented based on that support vector machine and corresponding prediction model was set up. To obtain the model coefficients, 18 groups of test data of CFG pile composite foundation were trained, the training value conforms well to the test value. Then the model was used to predict another 4 groups of test data. The result showed that the prediction value was close to the test value. The theoretical analysis and practical example indicated that the prediction method of bearing capacity of CFG pile composite foundation based on support vector machine is accurate and reliable.

Analysis on Bearing Capacity of CFG Pile Composite Foundation in Baotou

By uniting composite foundation with CFG pile composite foundation for a practical engineering project in Baotou, the bearing capacity of CFG pile in sandy soil and silty soil foundation were analyzed. The conclusion can be applied to the similar projects in the region of Inner Mongolia.

Research Progress and Development of CFG Pile Composite Foundation

This paper introduces the present research and observes the future research of CFG pile composite foundation.

Effect of cantilever soldier pile foundation excavation closing to an existing composite foundation

Adjacent high-rise building with CFG pile composite foundation was studied using model test method to investigate stress and displacement of the foundation pile retaining structure, the subsidence and transmogrification law of the composite foundation. Two different project cases with and without high-rise building adjacent to pile foundation were compared. The relationships of slope pile bending moment, earth pressure, pile top displacement and complex settlement with respect to time were obtained. 1) When there is no adjacent building, the displacement of supporting system caused by excavation is mainly in the horizontal direction; while when the adjacent building exists, the displacement of supporting system will be vertical. 2) When the excavation depth is less than or equal to the adjacent building’s composite foundation depth, the force of supporting structure is uniform and has small value, at the same time, the pile strength is in fully use and the foundation is stable; while when the excavation depth is greater than the depth of adjacent building’s composite foundation, the results will be opposite. 3) During the excavation process, the adjustment of the composite ground loads on the supporting structure is carried out downward and the force of the supporting structure is reduced through the deformation of the bearing layer.

CFG Pile Composite Foundation Reinforcement Mechanism and its Application in Engineering

Kunming dian chi lake to pick to: the main southern culvert-pipe CFG pile composite foundation, illustrates the application of CFG pile mechanism, design calculation, construction process and the detection principle and its application effect is analyzed.