The Influence Of PVDs’ Bending On Its Discharge Capacity And Single Well Test

It often appears hard crust lying during the reinforcement of vacuum preloading with plastic vertical drains(PVDs). Because of small transverse bending rigidity, it will bend PVDs in the range ofhard crust lying heavily, which will reduce discharge capacity of PVDs. And what’s more, it will influence the effect of reinforcement of deep soft soil.First of all, this paper proposes that the bending state has become PVDs’ normal state during working, due to the effect of rapid consolidation of the vacuum preloading.There will be large deviation between the actual situation and the theoretical consolidation degree when using thelaboratory result ofdischarge capacity in vertical state to design.Therefore, the reductioncoefficientof PVDs’ discharge capacity when bending should be taken into consideration to modify well resistance factor, which will make the calculation of consolidation degree closer to the actual situation.Second, in order to study the variation of PVDs’ discharge capacity when bending, make an iron-frame to achieve the bend of PVDs, study the changing rules of PVDs’ discharge capacity under the different forms of bending through test, and summarize the influence factors of discharge capacity. Using the concept of local loss coefficient of fluid mechanics, to build the quantitative relationship between PVDs’ bending angle and the local loss coefficient, and what’s further, to getthe fitting formula between local loss coefficient andreduction coefficient ofdischarge capacity.This paper designslaboratory single-well model tests with different vertical drainages, compare and analyze this two kinds of drain’s and sand wick’sdifferent effect of reinforcementby use of monitoring results. Get thereduction coefficientof discharge capacity through measuring the bending angel of PVDs after test, modify well resistance factor and calculate consolidation degree. Study the influence of bending on single well test, contrast it with the measured consolidation degreeand the pre-modifiedone, which can verify the accuracy of usingmodified well resistance factor.Finally, this paper puts forward some improvement measures for the test scheme, in order to research the PVDs’ bending discharge capacity more accurately, and make the results of test be closer to the engineering practice, which will be meaningful for the design of PVDs.