Foundation coefficient K30 test method of railroad subgrade built by coarse-grained soil

Abstract

The invention discloses a foundation coefficient K30 test method of a railroad subgrade built by coarse-grained soil. The test method comprises the following steps of: leveling of a field test surface, placing of a foundation coefficient tester, and preloading and progressive loading in a load test, and is characterized in that the specific method of the progressive loading in the load test comprises the following steps that: the progressive loading is carried out by taking the increment of each stage of load of 0.04MPa, and the load holding time after completing the application of the first stage of load is 2 minutes; starting from the second stage of load, the number of minutes of the load holding time after completing the loading of each stage of load is equal to the number of loading stages, and the subsidence of the stage of loading is recorded when the load holding time of each stage of loading meets the requirement; and the test is finished until the test termination condition of the foundation coefficient K30 test is reached. The method has the advantages of simplicity in operation, easiness in implementation, short required test time, high test efficiency and small test error, and can guarantee the correct judgment of compaction quality of the subgrade.

Description

technical field [0001] The invention relates to a geotechnical test method, in particular to a foundation coefficient K for railway subgrade compaction quality detection 30 experiment method. Background technique [0002] Reasonably and efficiently inspecting the quality of subgrade compaction is of great significance to ensure the quality of subgrade filling and improve construction efficiency. Since the construction of the Datong-Qinhuangdao heavy-duty railway in 1985, the foundation coefficient K has been introduced. 30 The test method has been widely used in the subsequent railway engineering subgrade filling and compaction testing. Currently, K 30 The index has become one of the main technical indicators of railway subgrades, and has been officially included in the "Quality Inspection and Evaluation Standards for Railway Subgrade Engineering" (TB10414-2003), "Code for Design of Railway Subgrade" (TB10001-2005) and "Code for Design of High-speed Railways ( Trial Impl...

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Problems solved by technology

[0004] In the current "Railway Geotechnical Test Regulations" (TB10102-2010) specification, during the step-by-step loading test, the subsidence increment within 1min is not greater than 1% of the subsidence of the level of load as the control standard for applying the next level of load (ie 1% deformation stability control standard), the purpose of which is to make the subsidence under each level of load as close as possible to the final settlement, that is, to apply the next level of load after 99% of the deformation under the level of load has been completed, This relatively strict deformation stability control standard is theoretically reasonable for truly and accurately reflecting the deformation resistance of the soil structure, but as a test method for subgrade compaction quality inspection that needs to be carried out at the road construction site, there are the following unreasonable Points: 1) It is necessary to record the sinking increment every 1 minute after the application of each level of load is completed, and calculate whether the percentage of the sinking increment and the weighing under the loading test of this level meets the 1% deformation stability control standard, so that the test The process operation is complicated; 2) According to the "High-speed Railway Design Specifications (Trial)" (TB10621-2009) the K 30 The value is not less than 190MPa / m and the K of the bottom layer of the bed 30 The value is not less than 150MPa / m (gravel and coarse gravel) or 130MPa / m (sandy soil and fine gravel), and the limit of test sinking is 1.25mm and the load increase of 0.04MPa per level The average subsidence under each level of load is about 0.2-0.3mm; for the foundation bed structure of the transition section filled with graded gravel and 3%-5% cement, the K 30 The value is even as high as 300-400MPa / m, and the average settlement deformation under each load is between 0.1-0.15mm

The corresponding 1% deformation increment in the two cases is about 0.001mm ~ 0.003mm, which exceeds the test accuracy of 0.01mm of the dial gauge. The use environment is harsh and not suitable for on-site construction environment, so it is extremely difficult to judge whether the 1% deformation stability control requirement is met, making it difficult to strictly implement this requirement on site

3) Under laboratory conditions, the K 30 Experiments show that: when K 30 When the values ​​are 214MPa / m and 380MPa / m, the sum of the load holding time to reach the 1% deformation stability standard under each load is 53.2min and 130min respectively, which requires a long test time and low test efficiency. In the process, it is necessary to wait for the inspection test to be completed and the inspection indicators to be qualified before the subsequent subgrade filling can be carried out. The waiting time for shutdown is long, which seriously affects the progress of the project

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