Abstract:
System and method for using an apparatus for measuring shear strength and viscosity of sediments that extend both the maximum rotational rate attainable and the maximum torque sustainable, and include a high data acquisition rate and data storage. The apparatus can accurately measure, for example, but not limited to, peak, evolution, and residual values of the undrained shear strength, yield, and viscous and plastic flow (including hardening and softening) characteristics of cohesive sediments at various pre-set and variable values of the rotational velocity of the vane sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of pending U.S. patent application Ser. No. 13/106,166 entitled HIGH-CAPACITY WIDE-RANGE VARIABLE ROTATIONAL RATE VANE TESTING DEVICE, filed on May 12, 2011, incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Devices and methods disclosed herein relate generally to testing devices, and more specifically, to vane shear testing devices. 
         [0003]    Vane shear testing devices are used in geotechnical engineering for determination of undrained shear strength, including undisturbed and remolded values. They are also used to study the effects of rotational rate on strength and as a tool for measurement of viscosity and other flow properties as a function of the rotational velocity or resulting strain rate in a variety of materials and sediments. The vane sensor is one of the main sensor configurations used in commercial rheometry products, for example, but not limited to, R/S Soft Solids Tester by BROOKFIELD® Engineering. Existing vane shear testing devices can be used, for example, but not limited to, (a) as handheld devices for rapid in-situ determination of the undrained shear strength of mostly surficial sediments in situ, and (b) in a bore-hole configuration in terrestrial and marine environments, for example, in FUGRO® Seaclam and FUGRO® Halibut systems. Additionally, vane testing can be used in the laboratory on sediment specimens retrieved in coring or drill cylinders. In this application, the sediment core is split either along its length or cut into several sub-sections normal to its long axis. Vane tests can be performed on the exposed soil surface utilizing a variety of vane devices. General engineering practice typically calls for testing for the strength parameters (undrained shear strength, residual/remolded strength) at a rotation rate of 60-90 deg/min (ASTM Standard. (2005)). See “D4648 Standard Test Method for Laboratory Miniature Vane Shear Test for Saturated Fine-Grained Clayey Soil.” ASTM International, West Conshohocken, Pa. 
         [0004]    Rheometers are tools similar to vane shear devices (in certain configurations) and are used primarily in determining viscous parameters of fluids. Some rheometers, for example, R/S Soft Solids Tester by BROOKFIELD® Engineering, are adapted for testing viscous and yield properties of soft solids by utilizing a vane-shaped sensor. These instruments, however, test materials that are not normally encountered in natural environments, for example, materials that are typical to geotechnical investigations of either terrestrial or marine sediments. Thus, these instruments can be limited in rotational velocity and maximum torque capacity. These limitations could make them insufficient for certain types of geotechnical media and specific testing conditions. Further, devices characterized by variable rate torque application can be limited by the maximum rotational velocity that can be attained and the maximum torque that can be applied, limiting the use of these devices, especially for applications such as impact penetration and burial of objects in marine sediments. 
         [0005]    What is needed is an apparatus for measuring shear strength and viscosity of sediments that extends both the maximum rotational rate attainable and the maximum torque sustainable, and includes a high data acquisition rate and data storage. 
       SUMMARY 
       [0006]    To address the above-stated needs, the present teachings provide an apparatus, method of making the apparatus, and method of using the apparatus for accurately measuring, for example, but not limited to, peak, evolution, and residual values of the undrained shear strength, yield, and viscous and plastic flow (including hardening and softening) characteristics of cohesive sediments at various pre-set and variable values of the rotational velocity of the vane sensor. The main purpose of the apparatus is to measure accurately undrained shear strength, yield, and viscous flow characteristics of cohesive sediments at various pre-set values of the rotational velocity of the vane or other sensor. The purpose is to extend the measurement ranges for the combination of torque and rotational velocity to beyond those achievable by any other currently existing research or commercial device available. 
         [0007]    The apparatus is intended for direct measurements and constitutive characterization of a variety of cohesive sediments. The apparatus consists of a base on which a vertical column is mounted. The vertical column includes a linear track on which a carriage plate mounts, facilitating the mounting of the head assembly and allowing for an easy set-up and adjustment of the measurement head position. The head assembly consists of a drive motor, rotary torque sensor, and the vane sensor for insertion into the sediment sample. The carriage slides on the vertical column linear track and is supported by a counter balance assembly that uses a constant tension spring having a spring force equal to the weight of the carriage and head assembly. The counter balance assembly allows the carriage to be easily adjusted vertically thus inserting the vane into the sediment sample with required accuracy in position and minimal distortion of the sediment. The apparatus incorporates a clamping system to support a variety of standard sample tubes in which the sediment sample is contained. The motor is controlled by a computer program that includes high speed data acquisition capabilities to measure and record the torque produced by the vane as a function of time. 
         [0008]    The apparatus is capable of testing a wide range of materials, from liquids, to semi-solids, and to solids of variable resistance to shearing, including, but not limited to, a wide variety of marine sediments. The apparatus is capable of testing at a high rotational velocity and acquiring data at a high rate. The apparatus is designed to receive sensor attachments, for example, conventional attachments manufactured by, for example, but not limited to, WYKEHAM FARRANCE™ attachments (W sensors) and BROOKFIELD® Engineering attachments (B sensors). The attachments can be coupled using, for example, adapters, and can include, for example, but not limited to, vanes, concentric cylinders, bobs, double-gap sensors, and cone and plate. 
         [0009]    The apparatus for measuring characteristics of sediments can include, but is not limited to including a sensor drive shaft coupled to a one of a variety of sensors, for measuring characteristics, a main measurement head applying a rotation rate of up to 4000 rpm to the sensor drive shaft and determining an undrained shear strength up to 230 kPa, and a computer, coupled to the main measurement head, collecting the characteristics while the rotation rate may be greater than 1200 rpm and the undrained shear strength may be greater than 6 kPa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram front and rear isometric views of an embodiment of the apparatus of the present teachings; 
           [0011]      FIG. 2  is a schematic diagram of elevation and plan views of an embodiment of the apparatus of the present teachings; 
           [0012]      FIG. 3  is a schematic diagram of exploded front and rear views of the column assembly of an embodiment of the apparatus of the present teachings; and 
           [0013]      FIG. 4  is a flowchart of the method of manufacture of the apparatus of the present teachings. 
           [0014]      FIG. 5  is a flowchart of an alternate method of manufacture of the apparatus of the present teachings; and 
           [0015]      FIG. 6  is a flowchart of the method of use of the apparatus of the present teachings. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The problems set forth above as well as further and other problems are solved by the present teachings. These solutions and other advantages are achieved by the various embodiments of the teachings described herein below. 
         [0017]    Referring now to  FIGS. 1-3 , apparatus  100  for measuring characteristics of sediments can include, but is not limited to including, main tower  109  attached to base plate  113 , main measurement head  104  connected to main tower  109  by constant load spring mechanism  107 , for positioning measurement head  104 , said main measurement head including a drive motor, a load cell shaft coupled with drive motor  103  and a sensor drive shaft within a drive shaft housing  135  via a coupler  117 , said load cell shaft including a load cell, a sensor  121  by attachment mechanism  115 B to the sensor drive shaft, and a vessel holding a sample, said sensor measuring characteristics of the sample. Sensor  121  supplies the measured characteristics to load cell  105 , and load cell  105  supplies the measured characteristics to a computer. Apparatus can optionally include an attachment holder coupled with attachment mechanism  115 B, special connector  101  rotatably coupling the base plate  113  with the main tower  109 , and screws  137  fixedly coupling base plate  113  with main tower  109 . Sensor  121  can be, for example, but not limited to, W sensors and B sensors. Main measurement head  104  can be configured to include torque load cell  105 . 
         [0018]    Continuing to refer to  FIGS. 1-3 , apparatus  100  for conducting testing of undrained shear strength of water saturated cohesive sediments as well as viscosity of a variety of soft solids and viscous fluids can include, but is not limited to including, main tower  109  attached to base plate  113 . Base plate  113  can be connected to main tower  109  by, for example, but not limited to, special connector  101  ( FIG. 3 ) that can allow for main tower   109  to be rotated to achieve various orientations with respect to mounting base  119 . Base plate  113  and main tower  109  can be, for example, fixed in position with screws  137 . Main measurement head  104 , which includes main motor  103  and torque load cell  105 , is connected to main tower  109  by constant load spring mechanism  107 , allowing for smooth and precise vertical sliding and positioning of measurement head  104  at a desired height. Load cell shaft (not shown) inside torque load cell  105 , is connected to drive motor  103  on the end nearest drive motor  103  and to a sensor drive shaft (not shown) located within housing  135 , and attaches at one end to the load cell shaft via coupler  117 . Torque load cell   105  can be, but is not limited to being, a T8 ECO series contactless torque loadcell, manufactured by Interface Co. (www.interfaceforce.com). The output of torque load cell  105  is via a DC voltage that can be acquired, recorded, and converted to engineering units via a calibration factor for torque. Torque load cell  105  can be connected to a data acquisition card, for example, via a switchboard in a computer. For example, a National Instruments DAQCard-6036E, which has a 16-bit signal resolution and can sample at 200 kHz, can be used. Coupler  117  can be, but is not limited to being, Elastomer Coupling manufactured by R+W Co. (www.rw-america.com). Couple  117  can include metal alloy housings with an elastomer inserts of various stiffnesses. These couplings can compensate for misalignment and vibration. Sensor  121  is attached, in the case of W sensors, by attachment mechanism  115 B. W sensors can be directly attached, whereas B sensors can be attached to attachment mechanism  115 B by a separate attachment (holder). Shown in  FIG. 1  is a W sensor being attached by attachment mechanism  115 B. To attach a B sensor, a coupler that fits over attachment mechanism  115 B is used, making it possible to attach a variety of B sensors. Coupler  117  appears on both sides of load cell  105 . On one side, motor  103  is coupled to the load cell shaft by coupler  117  to minimize off-axis forces of load cell  105  and an increase in torque measurement accuracy. Coupler  117  can be designed with elastomer inserts selected empirically to minimize off-axis forces. The attachment of sensor  121  to the sensor drive shaft (which is located inside housing  135 ) can be completed, for example, by direct attachment, using a built-in coupler for use with sensors including, but not limited to, WYKEHAM FARRANCE™ vanes, or by using an additional coupler that is attached to sensor drive shaft  115 B and allows for mounting all sensors available from, for example, but not limited to, BROOKFIELD® Engineering for the Soft Solids Tester and similar rheometers. The couplers securely fasten the vanes and other sensor attachments so that the sensor (or vane) will not disengage, decouple, or slip during testing. 
         [0019]    To operate apparatus  100 , a sample is fixed at the base of the instrument via one of several available options (depending on the type and the geometry of the sample). Appropriate vane (or other sensor) is attached to the matching coupler and then to the lower portion of the load cell shaft. The main measurement head with the motor, load cell, and the mounted vane (or other sensor) are then lowered into the specimen to the desired depth and fixed in place by tightening the screws on the slider part of the vertical tower assembly. At this stage the device is ready for testing. 
         [0020]    Testing can be conducted in a variety of ways, fully controlled via the LabView™ developed software package. This is generally (but not only) done under the conditions of the constant rotational velocity, set via the software interface at the desired value and not to exceed  4000 rpm (the motor limit). As the motor-vane assembly is turning within the specimen, load cell   105  is continuously measuring the torque. Data acquisition software is monitoring, recording, and storing the measured torque, which is generated by the resistance of the material being tested to movement of the sensor package (vane, bob, etc.). The data acquisition software is also monitoring, recording, and storing the motor parameters, including current velocity, and position. From these measurements, a variety of parameters of interest can be derived, including undrained shear strength, residual shear strength, viscosity, yield properties, and other as a function of time, current rotational velocity, or position of the sensor within the specimen. 
         [0021]    Apparatus  100  can improve measurement capacities, including maximum torque and maximum rotational velocity that can be achieved (see Table 1) and can improve the ability to handle a variety of specimen sizes and shapes, including traditional small specimens in boxes, beakers, core sub-sections, and similar vessels, fully split long cores positioned flat on the table (base plate), or full cores or long sections of cores attached to the main tower of the device when it is rotated to the full back position. This latter position allows for testing at ends of long cores without sub-sampling or splitting and without changing the preferred vertical orientation of the core (sampling tube). Table 1 shows a comparison of device capacities of the apparatus of the present teachings compared to alternative devices. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                   
                 Apparatus 
               
               
                   
                   
                 Perez- 
                 Biscontin 
                 of the 
               
               
                   
                 Locat &amp; 
                 Foguet et 
                 &amp; Pestana 
                 present 
               
               
                   
                 Demers ′88 
                 al. ′99 
                 ′01 
                 teachings 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Max rate, rpm 
                 500; 1200 
                 400 
                 100 
                 4000 
               
               
                 Max Su, kPa 
                 0.4, 0.05 
                 0.6 
                 6 
                 230 
               
               
                   
               
             
          
         
       
     
         [0022]    Referring now to  FIG. 4 , method  450  for manufacturing an apparatus for measuring characteristics of sediments can include, but is not limited to including, the steps of attaching  451  main tower  109  to base plate  113 , connecting  453  main measurement head  104  to main tower  109  by constant load spring mechanism  107 , connecting  455  load cell shaft inside load cell  105  in main measurement head  104  to drive motor  103  at drive end  105 A and to attachment end  105 B via coupler  117 , and attaching  457  sensor  121  to load cell shaft by attachment mechanism  115 B. Optional steps can include attaching W sensors directly to attachment mechanism  115 B, attaching B sensors to attachment mechanism  115 B using a coupler covering attachment mechanism  115 B, selecting the sensors from a group consisting of WYKEHAM FARRANCE™ vanes and BROOKFIELD® Engineering rheometers, connecting base plate  113  rotatably to main tower  109 , fixing base plate  113  and main tower   109  in position with screws  137 , and configuring main measurement head  104  with main motor  103  and torque load cell  105 . 
         [0023]    Referring now to  FIG. 5 , alternative method  500  for manufacturing an apparatus for measuring characteristics of sediments can include, but is not limited to including, the steps of rotatably  501  coupling tower  109  having proximal end  125  and opposing distal end   127 , having at least one bearing guide  126  extending from proximal end  125  to distal end   127  and base plate  113  assembly, with mounting plate  119 , coupling  503  measurement head   104  having motor  103  and torque load cell  105  with tower  109  at proximal end  125  using a connecting mechanism, motor  103  having a motor drive shaft, coupling  505  measurement head  104  with at least one bearing guide  126  and locking screw  114 , coupling  507  a load cell drive shaft with the motor drive shaft and with a sensor drive shaft via couplers  117 , and coupling  509  a sensor with the sensor drive shaft. Optional steps can include fixing base plate  113  in place with screws  137 , mounting height-adjustable specimen holder  133  on tower  109 , and mounting girth-adjustable specimen holder  133  on tower  109 . The connecting mechanism can be a spring mechanism, and the spring mechanism can be constant load. The couplers can be flexible. 
         [0024]    Referring now to  FIG. 6 , method  550  for using an apparatus for measuring characteristics of materials can include, but is not limited to including the steps of fixing  551  a sample at the base of the apparatus, the apparatus including main tower  109  attached to base plate  113 , a main measurement head  104  connected to the main tower  109  by a constant load spring mechanism  107 , the main measurement head including a drive motor, a load cell shaft coupled with drive motor  103  and a sensor drive shaft within a drive shaft housing  135  via a coupler  117 , the load cell shaft including a load cell, a sensor  121  configured to attach by attachment mechanism  115 B to the sensor drive shaft, a vessel holding a sample, the sensor configured to measure characteristics of the sample and the motor, the sensor configured to supply the measured characteristics to the load cell, the load cell configured to supply the measured characteristics to a computer, attaching  553  the sensor to the attachment mechanism and the load cell shaft, lowering  555  the main measurement head having the motor, the load cell, and the attached sensor into a specimen to a pre-selected depth, fixing   557  the main measurement head in place by tightening screws on a slider part of the main tower, setting  559  a rotational velocity, monitoring, recording, and storing  561  characteristics of the material and the motor sensed by the load cell, and deriving  563  undrained shear strength, residual shear strength, viscosity, and yield properties as a function of time and the characteristics. The characteristics can include, but are not limited to including, torque generated by the resistance of the material to movement of the sensor, motor current velocity, motor position, and motor torque. 
         [0025]    Apparatus  100  has, in comparison to existing technology, high torque capacity, high velocity, digitally controlled and monitored motor, high precision, infinite-rotation load-cell for accurate torque measurements at variety of speeds, load-compensated sliding head lift mechanism for easier and more precise placement of the sensor (vane) in the testing medium, rotating design for the main assembly tower, allowing for testing of small core sub-section and other specimens in small containers, full spit cores, and long upright positioned cores without sub-sectioning (main tower in rotated back position), high speed data acquisition and control system and software written using, for example, but not limited to, a LABVIEW® package, and the ability to accept different sensors, for example, but not limited to, via two specially designed couples, including standard WYKEHAM FARRANCE™ vanes, and sensors supplied by BROOKFIELD® Engineering R/S Soft Solids Tester (vane, concentric cylinder, cup and plate, etc.). Apparatus  100  can include, but is not limited to including, National Instruments DAQCard-6036 E (having 16-bit resolution, 200 kHz acquisition rate) and National Instruments LabView software. The commercial software is augmented by acquisition software in which data are acquired at a maximum rate of, for example, 200 kHz, and conditioned and time-averaged to manage natural fluctuations and noise. The acquisition software can increase data accuracy by filtering out or smoothing out the electrical noise. For example, using a moving average of 20 would yield approximately 0.42 data points per degree rotation at a maximum angular velocity of 4000 rpm. This corresponds to approximately a 2.4° rotation per measurement. In this example, the frequency of measurements is sufficient for accurate results in geologic materials. Apparatus   100  can also store the acquired and filtered/conditioned data on conventional mass storage devices (not shown). 
         [0026]    The present embodiment is directed, in part, to software for accomplishing the methods discussed herein, and computer readable media storing software for accomplishing these methods. The various modules described herein can be accomplished on the same CPU, or can be accomplished on different computers. In compliance with the statute, the present embodiment has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the present embodiment is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the present embodiment into effect. 
         [0027]    Referring again primarily to  FIG. 6 , method  550  can be, in whole or in part, implemented electronically. Signals representing actions taken by elements of apparatus  100   ( FIG. 1 ) and other disclosed embodiments can travel over at least one live communications network. Control and data information can be electronically executed and stored on at least one computer-readable medium. Components of the apparatus can be implemented to execute on at least one computer node in at least one live communications network. Common forms of a computer-readable medium can include, for example, but not be limited to, a floppy disk, a flexible disk, a hard disk, magnetic tape, or any other magnetic medium, a compact disk read only memory or any other optical medium, punched cards, paper tape, or any other physical medium with patterns of holes, a random access memory, a programmable read only memory, and erasable programmable read only memory (EPROM), a Flash EPROM, or any other memory chip or cartridge, or any other medium from which a computer can read. Further, the computer readable medium can contain graphs in any form including, but not limited to, Graphic Interchange Format (GIF), Joint Photographic Experts Group (JPEG), Portable Network Graphics (PNG), Scalable Vector Graphics (SVG), and Tagged Image File Format (TIFF). 
         [0028]    Although the present teachings have been described with respect to various embodiments, it should be realized these teachings are also capable of a wide variety of further and other embodiments.