1. Introduction

The pre-bored pile (BASIC) technology, widely developed and implemented in Japan since the early 1980s, is an innovative pile installation method designed especially for urban areas or sites with stringent noise and vibration control requirements. Unlike traditional driven or pressed piling, this technique partially replaces the in-situ material without creating significant compaction. This minimizes alterations to the natural stiffness and avoids excess pore pressure of soil during installation, making it ideal for sensitive environments.

The method operates by drilling a borehole larger than the pile diameter, then mixing the in-situ soil with cement grout to create a stabilized support mixture. The PHC pile is lowered into this cement-soil mixture before it sets, and the pile is rotated and pressed into the mixture to enhance adhesion. With maximum depths contingent on drill capacity (typically up to 40 m), this technique is effective on complex geological profiles, including karst formations and thick sand or gravel layers.

BASIC technology not only offers high technical efficacy but also provides cost savings and environmental benefits. Its exceptional versatility allows PHC piles to penetrate various soil conditions smoothly, ensuring project stability and safety, particularly in challenging geotechnical environments.

2. Scope of application

With the advantage of compact equipment and safety for adjacent structures, the pre-bore pile installation method is particularly suitable for projects with limited construction space, infill developments between high-rise buildings, or projects on geotechnically challenging soils containing gravel, clay pockets, or karst cavities. This method ensures minimal disturbance to the surrounding environment, making it ideal for areas where noise, vibration control, and maintaining the integrity of nearby buildings are critical.

3. Construction sequence

The installation sequence of pre-bored pile (BASIC) method is illustrated in Fig. 1.

Figure 1. Installation sequence of pre-bored pile (BASIC) method 

4. Technology video