Study On The Correlation Of Blow Counts Of Two Dynamic Penetration Testing Apparatuses Based On In-situ Tests

Geotechnical investigation,as an important link of engineering construction,is mainly based on the requirements of the construction project,to identify,analyze and evaluate the geological and environmental characteristics and geotechnical conditions of the construction site,and to prepare survey documents,so as to ensure the safety of engineering construction and design reliability.In situ testing technology is an important component of geotechnical engineering investigation.It tests the physical indicators of soil in its natural state and evaluates the engineering properties of the soil in the original location of the testing site,without disturbance or minimal disturbance.Cone dynamic penetration testing(DPT)and standard penetration testing(SPT)are commonly used in-situ testing techniques in engineering,which estimate soil mechanical parameters such as foundation bearing capacity through the number of blows penetrated.DPT and SPT tests have advantages such as simple equipment and operating methods,durability,speed,and economy.SPT tests are commonly used to evaluate the strength,deformation parameters,foundation bearing capacity,single pile bearing capacity,etc.of sand,silt,and cohesive soil.DPT test is generally used for mechanical stratification of site soil,evaluating the uniformity and density of the soil,soil strength,deformation parameters,foundation bearing capacity,single pile bearing capacity,etc.The two types of penetration test engineering have different purposes,but they have the same purpose in evaluating the engineering properties of the site.Establish a conversion relationship between the two blow counts to achieve complementary advantages of the two testing methods in engineering applications.Regarding the correlation between DPT and SPT blow counts,on-site investigation and testing methods were used to select different test sites in Tangshan City,Hebei Province and Xichang City,Sichuan Province.Standard penetration tests,heavy dynamic penetration tests,and shear wave velocity tests were conducted on site.Through on-site measurement of SPT and DPT blow counts,the conversion relationship between SPT and DPT blow counts is analyzed,and the correlation between blow counts and shear wave velocity is preliminarily explored.The main work and analysis results completed in the paper are summarized as follows:1.Select 13 test sites in Tangshan and Xichang regions,and conduct SPT and DPT comparative tests on each site,namely one point two holes.Complete 26 on-site test boreholes,obtain 26 geological profiles,test 348 sets of SPT and DPT data,and 26 sets of shear wave velocity data.Establish a database based on the correlation study of SPT and DPT hammer counts during on-site investigation and testing.2.Through the analysis of measured data,the correlation between the number of blows in the standard penetration test and the heavy dynamic penetration test was studied;In response to the discreteness of data points,a data screening principle was proposed to reduce discreteness,and the method of correcting the number of blows was adopted to verify the rationality of the data screening and correction methods for the number of blows.3.Studied the influence of soil depth on the conversion relationship between SPT and DPT hammer counts,discussed the adaptability and universality of the conversion relationship in different regions,and explored the adaptability of the conversion relationship between SPT and DPT hammer counts in different regions from the perspective of hammer count engineering applications.4.Through on-site experiments,the correlation between DPT blow count,SPT blow count,and shear wave velocity was studied.The differences in the correlation between blow count and shear wave velocity in different regions were preliminarily analyzed,and the influence of experimental data discreteness on the correlation between blow count and shear wave velocity was explored.