Abstract
To investigate the quality of dry soil mixing (DSM) columns in different soft soil areas of east China, a large number of laboratory test results and field test results of DSM columns were collected and analyzed statistically. Furthermore, a quality assessment method for DSM columns is proposed in this paper. The hardness description (HD), standard penetration test (SPT), unconfined compressive strength (UCS), and soil-cement column quality designation (SCQD) are used as assessment indexes. The statistical analysis showed that the test results of SPT, UCS, and SCQD were scattered, particularly in shallow ground. The mean values of the SPT blow count, UCS, and SCQD of the DSM columns decreased with depth: the greater the depth, the worse the quality of DSM columns. The quality assessment results showed that the proportion of the great quality columns was 64.84%, and the proportion of the unqualified columns was 1.4%. The proportion of DSM columns with great quality in the lagoon soft soil area was greater than in other areas. The proportion of unqualified columns in the lacustrine soft soil area was the largest. For all soft soil areas, the proportions of great quality, good quality, general quality, and unqualified soil decreased in that order. The quality assessment of 8627 DSM columns showed the proportions of great quality and unqualified were 64.84% and 1.4%, respectively. It was found that the greater the depth of the DSM column, the more unqualified DSM columns, and the more difficult it was to control the quality of DSM columns.
Highlights
The standard penetration test (SPT) blow counts of dry soil mixing (DSM) columns were widely scattered, in shallow ground, which indicates that the quality of DSM columns varied greatly
Except for the lacustrine soft soil area, the mean strength of DSM columns decreased as the depth increased
The test results show that the blow counts of SPT, unconfined compressive strength (UCS), and soil-cement column quality designation (SCQD) of the DSM column decreased as depth increased
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Gunther [15] developed a modified dry mixing method that injected water into the soil during the installation process. Evaluation of soil mixing in the field and in the laboratory has been done before by many researchers [16,17,18,19,20,21,22,23,24,25]. Puppala [27] presented the results of an international survey conducted for the quality assessment of deep mixed columns. This paper proposes an effective quality assessment method for comprehensive evaluation of the DSM columns. The quality assessment method is introduced first; the statistical analysis, laboratory test results, and field test results are presented. The quality assessment results of the DSM columns in different soft soil areas and the distribution of quality level are discussed
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