Ultra-soft Ground Improvement Using Air-Booster Vacuum Preloading Method: Laboratory Model Test Study

Abstract

The air-booster vacuum preloading (AVP) method has been adopted for the treatment of ultra-soft soil foundations, especially in land reclamation projects, but the air injection mode has not yet been studied. In this paper, the authors investigated the difference in improvement effect in laboratory tests of two different air injection modes, including variable pressure and constant pressure. The results show that compared with the constant pressure AVP (CAVP) method with constant air injection pressure of 75 kPa, the variable pressure AVP (VAVP) method with variable air injection pressure from 25 to 150 kPa has a better effect on ultra-soft soil improvement. Besides, if the final air injection pressure increases properly, and the air injection pressure increases with the times of air injections slowly, the soil improvement effect is significantly improved. Compared to CAVP method, VAVP method can fully utilize the air injection effect of pressurization by forming closed spaces and enhancing permeability by crack growth.

Recent Developments in the Vacuum Preloading Technique in China

“…The air booster vacuum preloading technique was proposed to solve the shortcoming of the conventional vacuum preloading technique in that the PVDs' drainage capacities were often reduced due to the clogging of the filter sleeves. The effectiveness of this method was verified by the field practices [31,32] and laboratory model tests [33][34][35]. The principle of the air booster vacuum preloading technique is schematically shown in Figure 10.…”

A comprehensive study on the effects of initial water content, suction magnitude, and drainage zone size on self-weight consolidation and vacuum preloading of soft soils and slurried mine tailings

“…In some projects, it is required to combine vacuum preloading with other improvement methods to achieve a specific degree of consolidation during a certain period of time. For example, electro-osmosis [18][19][20], dynamic compaction effort [21][22][23], heat preloading [24,25], geosynthetic encased stone columns [26,27], pneumatic fracturing method [28], flocculant treatment [10,29], lime treatment [8,11], and air booster systems [30][31][32] are the conventional techniques can be accompanied by vacuum preloading.…”

Guest Editorial for the Special Issue on “Soft Ground Improvement”

“…For these 11 papers [1][2][3][4][5][6][7][8][9][10][11] in this special issue, we would like to group them according to the ground improvement method being considered and then point out the key issue(s) investigated only in this editorial note. There are four articles dealt with new innovative techniques to increase efficiency of (vacuum) consolidation; four articles studied new technics of soft ground improvement using chemical/cement mixing method; one article studied replacement technique, one article investigated effects of microbial induced calcite precipitation on the strength and modulus of clays, and one article dealt with the site investigation using piezocone test for design of soft ground improvement.…”

“…(1) Consolidation techniques Article 7:87 [4] experimentally studied the effect of air injection mode on the performance of air-booster vacuum consolidation and suggested a way of step-wise increase air pressure during the consolidation process. Article 7:93 [8] studied the vacuum dewatering of slurry using prefabricated horizontal drain (PHD) and proposed a method for predicting the variation of drainage rate from the PHD.…”