After enforcement of Housing Quality Security Acceleration Act in 2000, ground survey has been performed in housing sites which had not normally performed previously. A Swedish Weight Sounding Test (SWS test) was mainly adopted for housing ground survey because of a costly advantage while it could not classify soil type in-situ. We performed SWS test attached with fricative sound sampling function and discussed its soil classification capability in this paper. The aim of this research is to make possible to classify a soil type without depending on test operator's experiences and skills, thus it is required to evaluate a metal-soil fricative sound objectively which is generated between test machine and soil during ground survey.
2. Evaluating method
It is difficult to use tone and tone quality for evaluating method because a natural frequency of a test equipment chassis was varied if the number of rods was different, therefore only loudness was focused. From this reason, sound pressure level (SPL) was used as a classification criteria, particularly effective value of SPL was used for field tests.
3. Model ground tests
We investigate influence factors on sound pressure level by model ground firstly, (1) It was confirmed that SPL values increased when rotational speed of test rod increased in the case of clayey soil, so we adopted 50 half turns per a minute which is recommended in Japanese Industrial Standard. (2) There are no differences in the test results between two test operators. (3) No significant differences of test result were seen in the saturated and unsaturated condition. (4) Effectiveness of density was small. We investigate relationships between SPL(EV) and soil type. These relationships are reference data for soil classification in field tests.
4. Field tests
Four sites of field test were performed in order to investigate a soil classification capability of SWS test attached with fricative sound sampling function. Standard Penetration Test (SPT) was performed in all sites and sieve analysis test was performed in two sites. The proposal SWS test can discriminate sandy soil from clayey soil clearly and identify humus soil layer. The test results of SWS test with fricative sound generally corresponded to the results of SPT except we could not classify soil type if a screw-point bump into gravels and boundary line of soil layer showed out of position each other.
5. Concluding remarks
The accuracy of soil classification by proposed SWS test was inferior to by SPT, however it is adequate for the housing ground survey in terms of a cost. Because the technique of evaluating the groundwater level has improved recently and the hardness and tightness of soil can be evaluated with the conventional Nsw value, liquefaction potential of the ground could be evaluating solely by the proposed SWS test if the accuracy of the soil discrimination of this technology can be further confirmed.