The Research Of Heavy Dynamic Sounding Rod Length Correction Issue

Dynamic penetration (DPT:dynamic penetration test) as a means of in-situ test site, with test equipment is relatively simple, the operation is easy to adapt to a wide range of soil types and more, high efficiency, and can be continuous penetration, etc., in engineering applications more widely. Measured penetrometer blow count required to be used to assess the geotechnical parameters were based on stem length reduction amendment. However, existing national norms and local norms on stem length and depth correction has hit number one value, such as "investigation of geotechnical engineering" GB50021-2001 (2009 edition), only gives the rod length of 20 meters within the correction factor. The actual production process, the dynamic penetration test or standard penetration degree has far exceeded the actual depth of 20m, even to 100m or more, for dynamic penetration depth exceeds the limit of how to fix is currently no uniform regulations. Theoretical foundation dynamic penetration can be divided into two parts, one is the elastic rod Newton collision theory as the theoretical basis, it is characterized by a long pole rod length correction factor increases and decreases. Another part is the elastic wave theory as the theoretical basis, it is characterized by a correction factor with increasing rod length rod length increases, and finally equal to 1.Combining engineering instance data, using numerical analysis software, to simulate the dynamic penetration test and simulate the results with project examples and references for comparison and summary. Research can also be used as a standard penetration test results corrected reference rod length.This paper includes the following aspects of the research work:(1) Measured by collecting large amounts of engineering data and conduct certain laboratory tests, field tests, study the physical and mechanical properties of the sand and gravel and sand, and related parameters;(2) This paper studies the general mechanism of heavy dynamic penetration test, basic technical requirements and engineering applications, the application analyzes the characteristics and parameters of heavy dynamic penetration test in engineering instance of sand and gravel soil amendments;(3) the use of numerical simulation software to build dynamic penetration models. Through the touch probe and the soil to determine the simplified model, and select the contact method touch probe and the soil between the final build the initial model. Then the numerical model based on spreadsheet data engineering examples, the results obtained for comparison with the actual project. Verify the feasibility of the model;(4) through sand and gravel, sandy soils of different simulation checking, get different soils in 2m,8.9m,16.4m,23.4m,30m,36m, curvilinear relationship with the correction factor when the rod length 50m. Get the degree of influence of different soil correction factor of rod length.