Development And Performance Evaluation Of One Curtain Traveling Pluviator For Reconstituting Centrifugal Testing Model

Geotechnical centrifuge test is recognized as one of the most advanced and ideal physical simulation test methods in geotechnical engineering and hydraulic engineering.The model preparation method is a basic and important link to ensure the accuracy and repeatability of test results.The pluviation method,also known as the falling rain method,can simulate the deposition process of natural sandy soil layer under the action of wind and water,and the mechanical properties of the model are very close to the natural foundation compared with other methods.A model preparation method commonly used in sand and ground test.However,the existing domestic sand and rain method devices are all funnel type,source automatic or static triaxial,resonant column and other test units.Although the development of mesh holes,duckbill,short-line and other types of sanding head,and added automatic,the pluviation function is still a “point” type pluviation method in the model preparation mode and working principle.With the increasing size and deep research of the geotechnical centrifuge test model,the funnel pluviation method has the defects of low exposure efficiency,large spatial dispersion,high compactness and poor repeatability.In order to meet the requirements of rapid increase of geotechnical centrifuge scale,low-density natural ground test and complex and refined model preparation,a new pluviation method with large flow,high precision and uniformity is developed,and the standardized and standardized geotechnical centrifugal test technology is improved.Scientific research output level has very important scientific significance and value.Based on the international first roller drive curtain pluviator developed by UC Davis,this paper analyzes the design difficulties and structural components of the curtain pluviator and proposes the key technologies of the core composition.And the system design method,established the theoretical relationship between design parameters and relative density,successfully developed the first set of curtain pluviator suitable for geotechnical centrifugal test.Compared with the funnel type device,the new device uses a plurality of rolling grooves to produce sand in parallel,and obtains a large flow rate;the falling sand is driven by the rotation of the drum,thereby avoiding the change of the sand position in the funnel and the influence of the sand block on the flow rate and the flow rate,and realizing the effect.High precision;walking in a straight line simplifies the “S” type walking path of the funnel pluviator,improving uniformity.Compared with the UC Davis device,the new device uses a continuously variable motor to drive the drum instead of the six-speed control,which improves the model preparation stability and accuracy.It increases the diameter of different diameter rollers and multiple rolling grooves,and expands the applicable soil and compactness.Degree interval.Through a series of mold tests and a variety of testing techniques,the advantages of the new device in the efficiency of production,the range of compactness and the uniform distribution were verified.The main work and innovations completed in this paper:1.Summarized the development history of existing pluviator at home and abroad and the structure and characteristics of different pluviator,and pointed out the shortcomings of the existing funnel pluviator and the key problems that need to be solved.The structural differences and advantages and disadvantages of the drum-driven curtain pluviator and the traditional funnel device are presented.The overall design ideas and key difficulties of the curtain pluviator are proposed.2.Based on the design difficulties and functional characteristics of the curtain pluviation method,the basic composition of the device is reasonably decomposed and the overall design scheme is proposed.According to the composition and design requirements of each part,the structural scheme and the determination method of key indicators are proposed.The design process and processing method of each part are elaborated,and the complete design theory of the curtain pluviator is established.3.Based on the relative density as the control target,the flow rate and the flow rate as the intermediate variables,the influence mechanism of the key control factors in the pluviation method was analyzed.The flow velocity and flow expression were derived and the influence of each key element on the relative density was given.Characteristics and trends;based on the influence trend and its relevance to design parameters,an optimized design and improvement method for new device control systems and power and transmission devices are proposed.4.The installation,commissioning and integration of various components of the device were established,and the expected function and design index of the device were realized.A series of tests and calibration tests were carried out for the new sand-rain device,and the influence of key control factors was given.The calibration curve is established for the preparation of the model;the relative density calibration and the microactuator taper resistance test results show that the prepared model has good pore uniformity and verifies the new sand-rain method.Main advantages and theoretical analysis results.