Method for discriminating sand-gravel stratum liquefaction through standard penetration test

Abstract

Provided is a method for discriminating sand-gravel stratum liquefaction through a standard penetration test. The method comprises the steps that a test sand-gravel stratum is drilled 5cm above the elevation of the test sand-gravel stratum; a standard penetration test device is connected and an injection device is put to the bottom of a drill hole after a connector of a feeler lever is inspected; then the injection device is driven into a saturated sand-gravel stratum by 5cm through a pilereing hammer, the standard penetration hammering number starts to be recorded for every 3cm of driving, and the total test range is 30cm and is divided into 10 test sections; a relation curve graph between the hammering number of each test section and the corresponding penetration degree is drawn, the invalid test sections affected by sand gravel of large grain sizes are removed according to the relation curve graph, and the standard penetration hammering number of 30cm of penetration is equivalently converted according to the standard penetration hammering number and the penetration degree of the valid test sections; and seismic liquefaction discrimination of saturated sand gravel is conducted according to the standard penetrate hammering number equivalent to 30cm of penetration into the saturated sand gravel. By adoption of the method for discriminating sand-gravel stratum liquefaction, the defect that in the prior art, the standard penetration hammering number tends to be large due to the effect of the sand gravels of the large grain sizes, and the seismic liquefaction discrimination result tends to unsafe accordingly is overcome.

Description

technical field [0001] The invention belongs to the technical field of in-situ tests, and relates to a method for judging the liquefaction of a sand and gravel layer by using a standard penetration test. Background technique [0002] More than 80% of my country's hydropower resources are distributed in the western region with frequent and strong seismic activities. Most of the river beds in this area have overburden layers, and there are often sand and gravel layers that may be liquefied under earthquake action in the overburden layers. With the implementation of the western development strategy, more and more earth-rock dam projects will be built on the sand and gravel covering layer in the future. The stability of the sand and gravel layer under earthquake action is an important issue related to engineering safety that must be considered. However, due to the large particle size of the gravel in the sand and gravel layer, when the standard penetration test is carried out in...

AI Technical Summary

Problems solved by technology

However, due to the large particle size of the gravel in the sand and gravel layer, when the standard penetration test is carried out in the sand and gravel layer according to the standard method, the standard penetration impact number is easily affected by the larger particle size of the gravel and is too large, resulting in the current standard When the standard penetration test method in the paper is applied to the liquefaction judgment of the sand and gravel layer, it will lead to unsafe results

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