Abstract
Results of laboratory testing of organic soil-cement samples are presented in the paper. The research program continues on the authors previously reported experiences with cement - organic soil sample testing. Over 150 compression tests have been carried out altogether. Several samples were cured for over 3 months before they were tested. Several factors, such as: the large amount of the pieces under test, long observation time, carrying out the tests in complex cycles of loading and the possibility of continuous registering the loads and deformation in the axial direction – made it possible to control numerous interdependencies, some of which have been presented in this work. Compressive strength and elastic modulus of cubic samples were examined. Samples were mixed and stored in laboratory conditions. The results clearly point to the fact that designing the DSM dry columns in the organic soil may be linked with a considerable risk and needs special precautions. During in situ mixing, the organic material surrounded by sand layers surely mixes with one another in certain areas. However, it has not been examined and it is difficult to assume such mixing already at the designing stage.
Highlights
Results of laboratory testing of organic soil-cement samples are presented in the paper
The typical Deep Soil Mixing (DSM) equipment consists of a binder injectors and a drilling machine, which are adopted to work in adverse soil conditions
Control procedures are generally similar to those designed for the DSM wet version, where the binder is injected in a liquid form [8,9,10,11,12]
Summary
As the DSM columns are mainly subject to compression, much more often than to bending or tension (which is more complex problem in terms of laboratory investigation). Using the uniaxial compressive test (UCT) we are able to observe lower strength results than during triaxial test. It means that we keep the safety margin for future design. In order to perform UCT, we put our specimen on a special circular pad and start pressing it by means of a slow movement of the upper part of the machine. Using the obtained results we are able to derive the chart of stress б1 [MPa] as a function of strain ε1 [%]. In the first phase of the uniaxial compressive test we can witness an almost-linear relation between stress and strain. That enables us to use approximation between two points and obtain linear modulus ( known as a Young’s modulus) E [MPa] by means of the relation (1):. 1 – difference between stresses for two subsequent points [MPa] 1 – associated difference in strains for the same points [%]
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