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What is Lime-Soil Compaction Piling?

February 26,2024

 Lime-soil compaction piling  and cement-fly ash-gravel (CFG) piling are innovative ground improvement techniques aimed at enhancing soil stability and load-bearing capacity. These methods are increasingly utilised in construction projects to address various ground conditions efficiently. Below, we delve into the specifics of each method, their application range, and the construction approach, providing a comprehensive understanding of these foundational solutions.

Lime-Soil Compaction Piles

Process and Application: This method utilises the lateral compression effect during the boring process, where the soil inside the pile hole is squeezed towards the surroundings, compacting the soil between piles. Subsequently, layers of lime-soil or plain soil (clay) are filled into the pile hole and compacted to the design elevation. It's particularly suitable for treating collapsible loess, fill soil, and miscellaneous fill above the groundwater level, with applicable foundation depths ranging from 5 to 15 metres. However, it's not recommended if the soil's water content exceeds 24% or saturation exceeds 65%.

Benefits: Lime-soil compaction piling offers on-site treatment, deep compaction, and utilises soil to treat soil, making it highly cost-effective and beneficial, especially in Northwest and North China for treating deep collapsible loess, fill soil, and miscellaneous fill foundations.

Cement-Fly Ash-Gravel Piles (CFG)

Process and Application: After boring holes with a long auger drill or sinking tube pile machine, a mixture of cement, fly ash, gravel, and stone chips with water is stirred and pumped or poured into the hole to form the pile body. CFG piling creates a rigid composite foundation, significantly enhancing bearing capacity and minimising foundation deformation. It is adaptable to various foundation types, including strip, isolated, box, and raft foundations, and is suitable for treating cohesive soil, silty soil, sandy soil, and self-weight consolidated fill soil. The applicability in sludgy soil should be determined by regional experience or field tests.

Construction Approach

Preliminary Pile Testing

Before compaction, a test piling process is carried out to determine the appropriate amount of fill and the number of tampings. This ensures the compaction coefficient of the pile body meets or exceeds 0.97, and the soil compaction coefficient between piles is no less than 0.90, guiding large-scale construction.

Pile Layout

Construction begins by precisely marking pile positions based on the design layout, using lime spots for identification and maintaining accurate construction records.


The boring sequence typically progresses from the centre of the route towards the sides, covering every 1-2 holes. A specialist records the process, ensuring the verticality of the pile tube is regularly checked and corrected if necessary.

Pile Formation

The lime-soil mixture is prepared and, after passing quality checks, transported to the site. The filling and compaction sequence follows a central to outward pattern, using a pear-shaped hammer for effective compaction.

Quality Testing

Upon completion, samples are taken to inspect the quality of the lime-soil compaction or soil compaction piling foundation. This includes reviewing construction records and testing the dry density of the pile body and the soil between piles, converting these to average compaction and compression coefficients. Load tests on the composite foundation are conducted to assess bearing capacity, with testing covering at least 0.5% of the total number of piles.