Smėlio tyrimai patobulintu dinaminiu penetrometru

Abstract

Grunto tyrimai atlikti ypač sunkiu DPSH-B tipo dinaminiu penetrometru. Šiuo penetrometru galima tirti įvairios granuliometrinės sudėties gruntų fizinę būklę, tačiau inžineriniuose geologiniuose tyrimuose daugiausia tiriami birūs gruntai. Bandymo metu gautų duomenų analizė yra sudėtinga, ypač tyrinėjant rišlius gruntus. Duomenų patikimumas priklauso nuo naudojamos įrangos savybių, zondavimo strypų ir grunto tarpusavio sąveikos bei nuo grunto reakcijos į smūgį. Tam, kad būtų galima įvertinti įrangos įtaką rezultatų patikimumui ir grunto reakciją į smūgį, dinaminės penetracijos metodą reikia tobulinti. Šiam tikslui dinaminio penetrometro kūgyje sumontuoti pagreičių matuokliai, o prie plakto pritvirtinta smūgio parametrus registruojanti įranga. Minėti įrangos patobulinimai leido detaliau analizuoti bandymo rezultatus. Šiame straipsnyje pateikiami pirmųjų tyrimų rezultatai ir gairės tolimesniems darbams.

The dynamic penetration test (DPSH-B) is one of a large amount of soil in-situ tests known. In world practice, this method is usually used for granular soil investigations although it can be applied in cohesive soils. Correlation of received DPSH-B test results with soil properties is complex and often not reliable. Especially it becomes obvious after application of cohesive soil analysis. In most cases, correlation depends on soil response to dynamic cone penetration and deformation of dynamic sounding equipment. Measurement of cone accelerations allows precisely evaluate the loss of hammer energy, displacement of the cone during strike, and etc. Correlation of DPSH-B (measured acceleration of the cone) and CPT test results are presented in this article. Studies of possibilities to determine other soil dynamic characteristics are presented too. During these studies, a super heavy dynamic penetrometer (DPSH-B) was used. The modified DPSH-B cone is made of very hard steel. The cone consists of two parts – a body and a screwed anvil. The body part is drilled for an accelerometer and a central processor unit (CPU). The anvil consists of a standard shape cone anvil, a thread to fasten the anvil into the body part and a cage for holding the accelerometer and CPU. The hammer displacement measurement equipment is made of a microprocessor, battery, Hall Effect sensors, SD card, and magnetic ruler. The DPSH-B test with a modified cone was carried out in a sandbox made of concrete walls and concrete bottom. The sandbox was about 5.0 m in depth and had about 25.0 m2 area. The studies have shown that the history of hammer impact and cone sinking helps to analyze the test data and to find correlations with soil properties, especially with dynamic characteristics. The groundwater influence in the values of cone acceleration should be examined very carefully, because this may have link with the dynamic pore water pressure.