Cement Pile Research Articles

A Review of Efficient and Low-Carbon Pile Technologies for Extra-Thick Soft Strata

With the development of urban underground space and increased infrastructure functions, both the scale of engineering construction and engineering difficulties have increased globally. In the construction of structures in soft strata, especially in coastal areas, the limited bearing capacity of the foundations poses a significant challenge. The composite pile technologies employing an organic combination of the rigid pile andthe flexible column can enable efficient soft ground treatment. In light of prominent global environmental issues, low-carbon energy-saving curing technologies have been rapidly developed for application in geotechnical engineering. This paper discusses progress in research on the mechanical properties of the efficient and low-carbon pile technologies, including the stiffened deep mixing (SDM) column, squeezed branch pile, pre-bored grouting plated nodular (PGPN) pile, precast cement pile reinforced by cemented soil with a variable section (PCCV), and carbonized composite pile (CCP). In addition, it reviews the technical characteristics and recent progress of feasible low-carbon energy-efficient curing technologies. The paper also proposes future directions for theoretical research and technological development of low-carbon pile technologies. The key contribution of this review is to provide insights into efficient and low-carbon pile technologies. In addition, the findings from the study of the pile technologies used in extra-thick soft strata also provide industry practitioners with a comprehensive guide regarding the specific applications and mechanical performance of the pile technologies, which can serve as a stepping stone to facilitate the technological development of the underground space industry.

Analytical Solution for Consolidation Behaviors of Combined Composite Foundation Reinforced with Penetrated PCCSs and Floating DM Columns

As the composite pile, the precast concrete piles reinforced with cement-treated soil (PCCS) is formed by driving the precast cement (PC) pile into the deep mixing (DM) column, which has been successfully and widely utilized to support buildings and embankments over soft soil. To increase the pile spacing and give full play to the economic merits of the PCCS, a reinforcement scheme, which involves the combined use of rigid piles and flexible columns, employing penetrated PCCSs and floating DM columns is proposed and utilized for soft soil ground treatment. However, there is a lack of feasible method for consolidation behaviors of this combined composite foundation (CCF) reinforced with penetrated PCCSs and floating DM columns under flexible loads. This paper developed an analytical solution to predict the average consolidation degree of this CCF based on a cylinder consolidation model and double-layer ground consolidation theory. The excess pore pressure and average consolidation degree were calculated by considering the composite pile penetration into the cushion. The analytical method agrees well with results obtained by numerical analysis. Additionally, a parametric study was conducted systematically to analyze the effect of key influence factors on the average consolidation degree of this CCF. The results indicate that the consolidation rate of this CCF can be much faster than that of the natural ground. The consolidation rate strongly depends on the compressive modulus and area replacement ratio of PCCSs. The increasing inner core-outer core modulus ratio and the inner core-subsoil modulus ratio increase the consolidation rate of this CCF. In addition, the consolidation rate increases with the gravel cushion-subsoil modulus ratio, while it decreases with the loading period.

Two-dimensional study of the inclusions of skirt sand and deep cement piles to improve the load‒displacement behavior of circular foundations on soft clay soil

The bearing capacity of clayey soils is low, and the induced settlements play an important role in estimating the stability of structures built on these weak soils. Therefore, these clayey soils need improved mechanical strength. In this study, a two-dimensional finite element model was used to improve the bearing capacity and settlement of soft clay soil by employing skirt sand piles, and the results were compared with reinforced cement piles. Skirt sand piles consisting of thick sand cores and closed tubes placed under a circular shallow foundation with a steel plate of suitable dimensions, as well as reinforced cement piles of different lengths and in nondrained situations were studied. These calculations were carried out using PLAXIS 2D software, and a series of finite element analyses were performed. The Mohr‒Coulomb and hardening soil models were used to model the fine-grained and granular soils, respectively. A linear elastic model was used to simulate the circular plate and skirt components. Previous experimental studies were used to validate the numerical model. The experimental test and the 2D axisymmetric model agree well. According to the assumptions, the efficiency of skirt sand piles is superior to that of deep cement piles. In addition, increasing the length of SSP skirt sand piles has a significantly greater effect on improving the bearing capacity than increasing the length of deep cement piles. As a consequence, the failure modes of piles with skirt sand were determined. It was found that the failure mode when skirt sand piles were tied into clayey soils occurred in the underlying sandy soil layer as a general shear failure.

A Practical Method for Calculating Soil Mixing Wall Retaining Structure by Means of a “Simple Beam Method”

SMW is the abbreviation of soil mixing wall. H‐type steel, also known as the new cement mixing pile wall, is inserted into the cement pile, which combines the bearing load with the impervious water retaining, and has the two functions of stress and impervious retaining wall of the supporting structure. In the design of conventional foundation pit engineering, the active Earth pressure calculated by Rankine’s theory is not consistent with the engineering practice because the soil behind the retaining structure has not reached the limit equilibrium state. The embedded depth and the horizontal supporting force of the retaining structure are usually calculated with the equivalent beam method, but the method is complicated. Taking the supporting structure of a foundation pit called “soil mixing wall retaining wall and bolt” as a case, in this paper, the lateral pressure is used to calculate the active Earth pressure at any depth, and the “simple beam method” is used to calculate the embedded depth, the horizontal supporting force, and the internal force of the SMW continuous wall, which intends to find out the first and second supporting points as the pivots of the “simple beam method” under the most unfavorable conditions. When the first pivot is used as the supporting point of the “simple beam method,” the soil pressure is ignored because it is within the critical depth of the Rankine active Earth pressure; while the second pivot is used as the supporting point of the “simple beam method,” the forces on it are balanced to the torque of the second pivot, only considering the moment balance of the active and passive Earth pressure on the isolation body under the second pivot point. The results are in good agreement with the results of the equivalent beam method and the measured values, and they are much closer to the measured values, which provides a practical method for designing SMW retaining structures.

Seismically safe parameters of confined blasting in levelling dry dock bottom

During construction of a dry dock, it became necessary to level the bottom of gneissic granite rock mass to 7 m by blasting. The blasting site appeared to be spaced at 8.5–20.0 m from a reinforced concrete caisson and a sand cofferdam reinforced with soil–cement piles. Aiming to ensure the required levelling at 16.2 m, the preset fragmentation quality and the reduced seismic safety, the parameters associate with the drilling-and-blasting pattern were calculated. The values of PPV caused by blasting-induced seismic waves in the caisson and cofferdam were found from the constructed formulas. The experimental measurement of ground vibrations induced by blasting used seismic recorder Vibracord DX. Al in all, 20 large-scale blasts were performed, and the blasted rock volume totaled 9 Km3. The comparison of the actual and calculated values of PPV in the caisson and cofferdam proves reliability of the presented formulas. It is calculated that PPV caused by the blasting-induced seismic waves at the farther wall of the caisson and at the nearest wall of the soil–cement piles are 2.0–27.0 mm/s and 2.0–22.0 mm/s, respectively, which is much less than the allowable PPV of 100–500 mm/s for the hydraulic engineering structures. It has been determined during blasting that the caisson preserves its integrity and no increase in the water inflow from the gulf is observed.

Liquefaction and Reliquefaction Characteristics of Aeolian Sand Foundation Reinforced by Precast Cement Piles Based on Shaking Table Test

With the continuous development of traffic construction, road engineering inevitably crosses the aeolian sand river valley area. Compared with general sandy soil and silty soil, cohesionless aeolian sand foundation has similar properties with fluid and higher liquefaction potential. Precast cement pile can greatly improve the vertical bearing capacity of foundation, but this paper finds that it also has antiliquefaction effect when it is used to reinforce aeolian sand foundation. In addition, there may be more than one liquefaction of aeolian sand foundation in areas with frequent earthquakes. Therefore, this paper explores the liquefaction and reliquefaction characteristics of aeolian sand foundation reinforced by precast cement piles through shaking table test. The test results show that under the excitation of 0.4 g EL Centro wave: (1) the increase of pore pressure in aeolian sand foundation will have multiple instantaneous peaks, which will promote the surface to float or sink. The phenomenon will be weakened by multiple earthquakes or pile reinforcement. (2) The prefabricated cement pile can improve the liquefaction and reliquefaction resistance of aeolian sand foundation. The effect is the best in the shallow layer of the foundation, which is increased by more than 30%, and the deeper the buried depth, the lower the effect. (3) The antiliquefaction ability of foundation will be improved after strong earthquake, but the dynamic response will be significantly increased in the next earthquake. (4) When the aeolian sand foundation reinforced by precast cement piles is reliquefied, the main frequency of the foundation will migrate to low frequency. The liquefied layer will inhibit the low frequency (2 ~ 15 Hz) energy transfer and promote the high frequency (25~30 Hz) energy transfer. The results provide reference for antiliquefaction design of aeolian sand foundation and improve the application of precast cement pile in liquefied foundation.

Regional-scale investigation of pile bearing capacity for Canadian permafrost regions in a warmer climate

Climate change is being experienced particularly intensely in the Arctic and therefore adaptation of engineering systems for this region cannot be further delayed. However, one of the major barriers to studies focused on adapting northern engineering systems is the lack of information at the spatial and temporal scales required for engineering applications. This study investigates pile bearing capacity for selected pile configurations for the Canadian permafrost regions (Nunavut and Northwest Territories), for current and future climates, using the very first ultra-high resolution (4 km) climate change simulation developed for the region using the Global Environmental Multiscale (GEM) model, for a high emission scenario.Comparison of the ultra-high-resolution GEM simulation, driven by reanalysis, with available observations confirms the model's ability in representing near-surface permafrost and related climate variables. The estimated adfreeze contribution to the total bearing capacity, for current climate, informed by the reanalysis-driven GEM simulation, for a 5-m cement pile, is found to be of the order of 15% for regions with shallow bedrock and 80% for regions with deeper bedrock. Application of the GEM climate change simulation outputs, for RCP8.5 scenario, suggest decreases to adfreeze contribution in the 5–30% range by 2040, with the largest differences noted for regions with deeper bedrock. For steel piles of same configuration, although the adfreeze contributions are only about 70% of that for cement piles, the projected relative changes are of similar magnitude.Further downscaling to 250 m resolution using the land model of GEM for the Slave Geological-Grays Bay corridor, where future developments are planned, including an all-season road, enables better estimation of bearing capacity for realistic pile scenarios such as those for bridges (in thick layer of sediments) used for river crossings. Due to the wide variation of pile materials, lengths and installation methods, site specific information can be developed from the framework developed in this study. The results of this study, including the ultra-high resolution climate change information, will thus form the basis for additional detailed investigations on climate-infrastructure interactions and climate resiliency studies.

ПОДБОР РАСХОДОВ МАТЕРИАЛОВ ДЛЯ СОЗДАНИЯ ГРУНТОЦЕМЕНТНЫХ СВАЙ В СЛОЖНЫХ ИНЖЕНЕРНО-ГЕОЛОГИЧЕСКИХ УСЛОВИЯХ

Strengthening of soils by jet technology in difficult ground conditions has now become widespread, including in the construction of buried and underground structures. At the same time, a sufficient amount of experimental data has accumulated to predict the properties of the resulting soil cement. The purpose of the work is to determine the optimal consumption of materials for soil-cement structures, taking into account complex engineering and geological conditions. The study of mineral-based hardening systems in water-saturated soils with inclusions of organic deposits or in conditions of high filtration has a number of features that make it difficult to assign optimal technologies and components of cement-based solutions for the formation of soil cements. To determine the final parameters of soil cement, the parameters of soil cement piles at the facilities during the construction of the subway, laboratory data on mixing mineral components and soils of different types, scientific and technical data were analyzed.

Retaining Technology for Deep Foundation Pit Excavation Adjacent to High-Speed Railways Based on Deformation Control

Considering the deep foundation pit of a car dumper room close to the Beijing–Baotou railway, the countermeasures of the foundation pit design are analyzed according to the surrounding environment and stratum conditions. Through Midas GTS software as well as field measured results, the construction effect on the adjacent railway subgrade is discussed. Therefore, the deformation characteristics of the foundation pit as well as the retaining structure, including the railway subgrade, caused by the excavation process, are revealed. The results show that the five-sided water-stop structure formed by cement piles around and at the bottom of the pit avoids the consolidation settlement of the adjacent railway subgrade caused by deep dewatering and also reduces the lateral displacement (i.e., in a horizontal direction) and the heave of the pit bottom. As a result, the lateral displacement near the railway side is larger than that of the retaining structure on the other side due to the subgrade on the pit side. The cross-lot bracing across the foundation pit will transfer the bias pressure of the subgrade to the retaining structure far away from the railway, while the transfer effect of the knee bracing is not obvious. The deformation of the railway subgrade and its evolution rate caused by the removal of internal bracing is significantly greater than the subgrade deformation and the change rate of deformation caused by excavation. The research results provide useful guidance for the deep foundation pit design.

COMPARATIVE ANALYSIS OF TECHNOLOGIES OF MICROPILES ARRANGEMENT DURING STRENGTHENING OF WEAK SOIL BASES

Purpose. Perform a comparative analysis of drill and injection (jet-grouting) and drill and mixing technologies of micropiles arrangement of weak soil bases with the identification of technological features that significantly effect on the design and calculation of weak soil bases strengthening. Methodology. To solve this problem, was conducted of the detailed analysis of the most effective methods of micropiles arrangement during the strengthening of weak soil bases (physical immersion, bored and packing of concrete, drill and injection of ground, drill and mixing soils and application of special effects). Peculiarities of technological parameters of jet-grouting and drill and mixing technologies are considered in detail. The advantages and disadvantages of each of the technologies are revealed. It is proved that the drill and mixing technology has a greater degree of prediction of the stress-strain state change of the inhomogeneous base. To determine the influence of deformation characteristics, a spatial finite-element model based on a flat prototype was created, which was built using automatic triangulation of the professional calculation complex SCAD. Findings. A significant reduction of the deformed state at an almost constant stress state is obtained. When the deformation characteristic increases by 3 times (the ratio of the modulus of elasticity of the soil cement pile and the weak soil), the vertical displacements of the foundation decrease by 1.23 times. Originality. It consists in obtaining the dependence of the change of vertical displacements and stresses on the modulus of elasticity of the soil cement micropile, created on the basis of drill and mixing technology. Practical value. It consists in the obtained results of comparative analysis of substantiation of micropile installation drill and mixing technology during strengthening of weak soil bases with definition of technological features and choice of drill and mixing as the most effective variant from the point of view of technology realization.

Influence of Basalt Fiber-Reinforced Cement-Based Composite on Slope Stability

Slope instability may be caused by the action of external load or the lack of internal shear strength. The traditional limit equilibrium method cannot accurately calculate the safety coefficient of slopes enhanced by fiber-reinforced cement piles. Few scholars have discussed the anti-slip property, structural form, and design calculation of fiber-reinforced composite cement piles. Therefore, this paper chooses to analyze the influence of basalt fiber-reinforced cement-based composite (BFRCBC) on slope stability. On the one hand, the authors analyzed the anti-crack mechanism of BFRCBC: the strength analysis was carried out by the rule of mixtures, the anti-crack analysis was implemented by the fiber spacing theory, and the entire anti-crack process was discussed in details. On the other hand, the authors constructed a slope model, and performed the relevant stability analysis. Experimental results show that the BFRCBC cement piles can effectively enhance the stability of the slope.

Feasibility for the implementation of cement piles

The article considers the technical and economic efficiency of the construction of pile foundations by the mixing method with mechanical activation of soils. Various designs and technologies for the construction of pile foundations are analyzed. The main most promising technological processes for the manufacture of pile foundations are described. The advantages of constructing pile foundations by a mixing method with mechanical activation of soils are substantiated. The results of calculations of comparing technical and economic indicators for the construction of types and designs of foundations are presented. Conclusions and recommendations on the construction of foundations of low-rise buildings are given.

Application in Cement Soil of Stabilizer in Silt Soft Soil of Wuxi in China

ABSTRACT Lu, X.; Cui, M.; Wang, P., and Li, B., 2018. Application in cement soil of stabilizer in silt soft soil of Wuxi in China. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 316–323. Coconut Creek (Florida), ISSN 0749-0208. Soft silty soils are widespread on floodplains and have a high natural water content, void ratio, weak permeability (10–10 cm/s), high strength, and low compressive engineering characteristics. Therefore, taking necessary action in areas where these soils are present is vital because they pose tremendous risks to the reliability of engineering. In this paper, the intensity variation rule of cement pile mixing in soft soil on the Wicheng Road, in the city of Wuxi, China, was studied under various unconfirmed compression strength tests, and with different stabilizer mixing agents and ages. For convenience to application to solidified soil engineering, we also confirmed a 28 day predictive mod...

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

Investigation of Performance of Soil-Cement Pile in Support of Foundation Systems for High-Rise Buildings

This paper presents the experimental study of Soil-Cement Pile (SCpile) by wet mixing method in sandy soils, with the typical project at An Trung Complex apartment, Da Nang city, Vietnam. With the characteristic of soil layers is sandy soil, the strength of laboratory stabilized soils with the amount of cement from 150¸300 kg/m3 was determined. Simultaneously, the authors also performed the experiments of 20 test piles collected from the site which has cement content about 280 kg/m3 and the unconfined compressive strength qu= (4.5-6.0) MPa. After that, a full-scale model static axial compressive load tests of two single piles and a group of four piles with diameter 800 mm and 12 m length were also conducted. The experiment results show that the bearing capacity of every single pile is 1.200 kN with settlement 6.93 mm and the group of four CSpiles is 3.200 kN with settlement 5.03 mm. The results presented in the paper illustrate that SCpile is the suitable solution for foundation construction process with low cost and saving time for high rise buildings. The result shows a capable application of soil cement piles for support of high-rise buildings.

STUDY OF THE EFFECT OF SOIL CEMENT ELEMENTS WHEN STABILIZING ROADBED MODEL IN LABORATORY CONDITIONS

Purpose.Experimental studies allow determining th estress-strain state or bearing capacity of the tested soil body. A preliminary study of the results of model testing and experimental research allows us to find the optimal solutions and to justify the parameters of the chosen technology. The purpose of this work is to determine the effect of soil cement elements when stabilizing the roadbed on a weak subgrade using the soil tests in laboratory conditions. Methodology. During the development of measures for the reconstruction and consolidation of soil bodies, their strength is tested using many methods. In all cases, we take into account the physical and mechanical characteristics of soils obtained as a result of research, as well as the existing regulatory documents. We performed the experimental studies by model testing in laboratory conditions. The model testing was based on the corresponding relationships between geometric sizes, mechanical properties of materials, loads and other factors on which the stress-strain state depends. During testing, the model was loaded gradually. We maintained each load level up to conditional stabilization of the soil deformation. We took the readings from measuring devices at each stage of loading after achievement of stabilization of soil mass deformations. We fixed the readings in the test journal. Findings. During stabilization with soil cement piles there is an improvement in mechanical properties, which leads to a decrease in deformations by 2…3.5 times. Each test is accompanied with graphs of relative deformations-stress dependence, as well as deformation curves and compression curves. According to the results of experimental stu-dies, it can be seen that when testing a model with cement piles, compared with a model without soil cement piles, the relative deformations of the samples taken prior to the experiment and after the experiment almost coincide, indicating a decrease in deformability under load. Originality. We proved that this stabilization type positively affects the stress-strain state of the soil body, by increasing its physical and mechanical characteristics. The obtained results allow for rational design of subgrade stabilization work with the help of modern technologies.Practicalvalue. The in-depth analysis of the results of experimental studies opens up possibilities for theoretical synthesis and development of theoretical foundations, which will allow in the future avoiding, in the similar cases, the experimental verification of the stabilization type given for the relative type of soil. It is confirmed that this method of stabilization used can be applied in real conditions.

Analysis of Causes of CFG Pile Necking in Saturated Soft Soil Layer and Its Control Measures

In recent years, composite foundation technology has been widely used in foundation treatment. Composite foundation theory has become an important research topic in the field of geotechnical engineering. CFG pile (Abbreviation of cement, fly ash, and gravel pile) in composite foundation is one of the commonly used technologies. It has advantages such as simple construction, reliable quality and low cost. When it is used in soft foundation treatment, it significantly improves the bearing capacity, reduces settlement, and turns waste (fly ash) to treasure, which benefits economic and social significantly. During construction, various defects in construction quality will affect the effect of soft foundation treatment. CFG pile necking is one of the more representative quality defects. This paper combined some project examples to analyze the causes of CFG pile necking and develop effective control measures for it which has a certain reference value towards the quality control of the technology

PRELIMINARY STUDY OF SOIL-CEMENT PILING AS A NEW ALTERNATIVE IN LEVEE AND RIVER BANK STRENGTHENING

Malaysiahas not yet experienced a totally severe levee failure as what have happened in other countries. However, flood has always been the major problem inMalaysiacaused by several factors including weather condition, man-made and also including levee or bund failure. Therefore, in order to produce a new alternative to improve the structures of levees and river banks, this study on preliminary investigation of soil-cement piling is done to see the possibility of it to be used in the strengthening of levee or bund and river banks. The investigation focused on determining suitable soil-cement ratio to produce soil cement pile encased in PVC pipes in terms of axial capacity. The results show that the soil-cement mixture with 11% cement ratio produced the reasonable pile axial/compressive capacity.

Characteristics of slag fine-powder composite cementitious material-cured coastal saline soil

Cement pile as slope support is used in a thermal coal storage and distribution base project in Caofeidian district. Taking into account the potential hazards of cement-cured saline soil, this research concerns a new type of coastal saline soil-curing agent to explore methods to prohibit the hazards of soluble ions in saline soil. On the basis of compressive strength, scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction analysis and a series of experiments, the strength, water stability, resistance capacity to seawater corrosion, microstructure and hydration products of slag fine-powder composite cementitious material (SM) agent-cured saline soil have been studied. The test results show that the curing agent reacts with Cl− in saline soil and generates a hexagonal plate crystal and needle-like Kuzel’s salt crystal, and thereby the strength of cured soil is increased with the absence of certain potential hazards of saline soil.

A Field Experimental Study of Composite Foundation with Rammed Soil-Cement Pile in Collapsible Loess Area

Natural foundation in loess areas is collapsible; however, composite foundation with rammed soil-cement pile can be used to meet the load requirements of the building. Immersion-compression test and field static loading test were carried out to measure the treatment effect. The test results showed that: the collapsible of loess foundation can be eliminated by treatment with rammed soil-cement pile when the loading pressure is between 200 to 500 kPa. Engineering properties of the foundation soil between piles are improved. The parameters improve more obvious with the pile spacing getting smaller. The bearing capacity of composite foundation increased to 291 kPa, compared with natural loess foundation. The research results can be applied to design and construction of compacted soil cement pile composite foundation in loess area.