Abstract:
A method and system for inducing a planned or controlled avalanche is disclosed. The system includes one or more sources of vibration mounted within a mass which is mounted within an aperture in the ground in the area where an avalanche has been determined to be likely to occur. One or more sensors is mounted between the source of vibration and the avalanche area (spaced from the vibration source), then the vibration source is operated at different frequencies to determine which frequency transmits the greatest force through the intervening terrain. Based on the analysis of the forces sensed at a distance from the vibration source, the best frequency for operation of the vibration source is determined and that frequency is used. Periodically, the process of testing the frequency versus force can be reviewed and the operating frequency adjusted. The present method and system envisions a plurality of vibrational sources arranged in a spaced array and uses more than one vibrational source to trigger a single avalanche at a desired time.

Description:
CROSS REFERENCE TO RELATED PATENT 
       [0001]    The present patent application is a continuation-in-part of my co-pending patent application Ser. No. 13/176,723 filed Jul. 5, 2011 and entitled “AVALANCHE CONTROL SYSTEM AND METHOD”. The specification and drawings of that patent application, which is sometimes referred to herein as the “First Avalanche Patent”, are specifically incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a method of (and system for) inducing a planned (or controlled) avalanche in a region in which an uncontrolled avalanche of snow might occur. That is, a controlled avalanche may be induced at a time which is most convenient and as frequently as desired to avoid a large avalanche at an undesirable time. 
         [0004]    2. Background Art 
         [0005]    Ski slopes, roadways, housing and railways through canyons are at risk of an uncontrolled avalanche in some areas. An avalanche can occur spontaneously when a snow pack is unstable and there is enough vertical angle. Areas where the instability is the greatest are known as avalanche “birthing” areas 
         [0006]    Naturally occurring avalanches are somewhat predictable, yet difficult to control. It is well known that earthquakes have caused several of history&#39;s great avalanches. Snowmobile riding in an avalanche-prone area has a propensity to initiate an avalanche, since the drive causes vibration which may make disturb the snow pack. 
         [0007]    It is sometimes desirable to provide a controlled avalanche at a desired time in some situations. That is, it is desirable to have more, smaller avalanches than fewer, larger avalanches. Further, it may be desirable to have an avalanche at a time when few people or animals are present in the area below an avalanche-prone area, for example, in the early hours of a day while many are asleep or when ski facilities are not operating. Also, if the approximate time of a planned or controlled avalanche is known, precautions can be taken for that time, such as closing of roadway or trails in the affected areas or otherwise warning those who could be in an area to avoid the area. 
         [0008]    Various approaches have been suggested to induce a controlled avalanche to mitigate uncontrolled avalanche events. One approach to causing a controlled avalanche has been to use a concussive event to trigger a planned avalanche, for example, using artillery ordinance, dynamite or a mortar shell. More recently, gas explosions in one of a variety of types have become popular to initiate an avalanche. For example, a fixed concussive device igniting explosive gases is one such system for using a gas explosion to initiate an avalanche, while a “Daisy Bell” concussive device carried by a helicopter is another such device which can initiate a controlled avalanche. 
         [0009]    The use of ordinance, dynamite or a mortar shell requires special handling skills and storage and is the subject of increased regulation due to safety concerns. 
         [0010]    One must also consider that some systems for initiating a controlled avalanche do not work well during times of heavy snowfall, such as those which require a helicopter. Operating a helicopter usually requires some visibility of the surroundings, while a heavy snowfall obscures the visibility of the pilot of the helicopter. So, in times when the risk of an uncontrolled avalanche increases (during heavy snowfall), a control system which uses a helicopter is less likely to be usable for that purpose. 
         [0011]    Some of the systems of initiating a controlled avalanche are relatively costly to use—for example, the Daisy Bell system requiring a helicopter and pilot. 
         [0012]    Additionally, some of these prior art systems employ elements and/or compounds which can be harmful to the environment, including the water supply. Various materials contained in explosives are toxic to people and/or animal and tend to remain in the water supply long after a triggering of the explosive, polluting the water supply and causing harm to those who use the water supply, directly or indirectly. For example, many explosives include aromatic hydrocarbons such as toluene as a component (for example, TNT) and toluene is a long lasting material which does not break down quickly and which is harmful to life, even in relatively small doses. Some of these materials are relatively soluble in water, while others are relatively insoluble in water, making the impact on the environment hard to predict, either regarding the short-term impact or the longer-term impact. 
         [0013]    Accordingly, it will be appreciated that the prior art system for inducing an avalanche have undesirable disadvantages and limitations. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention overcomes some of the disadvantages and limitation of the prior art systems for inducing a planned or controlled avalanche of snow in those areas which have been identified as prone to avalanche activity. 
         [0015]    The present invention allows for creating many small controlled avalanches to reduce the risk of a larger, uncontrolled and unpredictable avalanche. 
         [0016]    The present invention would also appear to be “friendlier” to the environment in avoiding undesirable chemicals and inconveniently-timed avalanches which may jeopardize lives. Further, since an avalanche may close roadways and other accesses, it would be desirable to “schedule” such avalanches at a time which is convenient (like the dead of the night), rather than allowing such events to occur naturally at an inconvenient time such as at a time of peak activity. 
         [0017]    The present invention includes a method of setting up a vibrational system to induce a controlled avalanche at a desired time. 
         [0018]    The present invention also allows for the system to be tuned to compensate for differences in the ground surrounding an avalanche-prone or avalanche birthing area. The tuning can also compensate for variations in the attachment of one or more vibration-inducing sources with the surrounding ground. 
         [0019]    The present system for inducing a controlled avalanche also appears to be relatively inexpensive to use (and reuse) and provides a minimal environmental impact, especially compared with alternate systems for creating an induced avalanche. This system also has the advantage that it can be operated in almost any kind of weather, not being dependent on moving people or equipment to the site of the desired avalanche. 
         [0020]    Other objects and advantages of the present invention will be apparent to one of ordinary skill in the art in view of the following description of the invention, taken in combination with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a pictorial representation or a perspective view of an area of an avalanche-prone area, showing one arrangement of system for inducing a controlled avalanche including a vibration unit; 
           [0022]      FIG. 2  is an enlarged view of a portion of  FIG. 1 , looking generally downward on an avalanche prone area having a plurality of vibration units (or sources) mounted in an array; 
           [0023]      FIG. 3  a cross sectional view of an system for creating vibration used in the avalanche-prone area of  FIGS. 1 and 2 ; 
           [0024]      FIG. 4  is a flow chart of one process useful in the present invention; and 
           [0025]      FIG. 5  is a cross sectional side view of one vibration unit useful in the system of  FIGS. 1 and 2 ; and 
           [0026]      FIG. 6  s a top view of the vibration unit of  FIG. 5 , with its top cover removed. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]      FIG. 1  shows a pictorial representation of a mountainous area  10  in which avalanches can be expected. The mountainous area  10  includes a plurality of peaks  12 ,  14  and  16 , with an avalanche origin region  20  defined between the lines  14   a  and  14   b  delineating an avalanche-prone area. The avalanche origin region  20  (sometimes alternatively called an “avalanche-birthing” or “avalanche-prone” area) often has a substantial terrain slope, perhaps averaging approximately 40 degrees, and is located within a terrain area in which the slope of the terrain is generally more gentle. A plurality of vibration sources  30  are mounted within the avalanche prone area  20  in accordance with the present invention. These vibration sources  30  may be generally of the type described in the First Avalanche Patent referred to above and incorporated herein by reference or use other similar systems for producing vibration. 
         [0028]      FIG. 2  shows an enlarged version of the avalanche-prone region  20  between the lines  14   a  and  14   b  of  FIG. 1 . A plurality of vibration sources  30  are indicated by the reference numerals  30   a  through  30   j.  Surrounding one of the vibration sources  30   a  are a plurality of vibration sensors  40   a,    40   b,    40   c  and  40   d.  Each of these vibration sensors is an instrument which measures the movement of the ground nearby the sensor and may be an accelerometer or a seismic sensor of the type used to detect, measure and locate earthquakes. Such accelerometers or seismic detectors are commercially available devices which are readily available and provide a time-varying electric signal representative of the displacement (or vibration) of the earth in the immediate area. 
         [0029]      FIG. 3  shows a flow chart of one method of using the vibration equipment of the present invention. The process starts with the assembly of one or more vibration units (as described later in this document) at block  110 . Next, the one or more vibration units are installed in the ground at block  120 . This is accomplished by providing an aperture in the ground in the approximate shape of the cross section of the vibration units, a little wider and deeper than the unit to allow it to fit in the ground conveniently with little clearance (and, as will be discussed later, the vibration unit(s) may be secured in place with an adhering material—such as concrete or cement—to provide a better vibration-transmitting connection between the vibration unit and the ground). While it is desirable to have the top of the vibration units below the surface of the ground, it is also desirable to have the vibration units not buried too deep in the ground to allow each vibration unit to vibrate the upper layers of the adjacent ground and to transmit the vibrational forces outward to the extent possible, rather than downward (into the ground). At block  130  the next step is to calibrate at least one (or each) of the vibration units (see discussion below, especially in connection with  FIG. 4 ). The vibration units can also be re-calibrated periodically to adjust for any changes in the units and/or the surrounding ground, perhaps as a result of ground changes, avalanches or belt tension or as a result of the seasonal weather cycles where the ground heats during the summer and cools during the winter, possibly changing the characteristics of the ground around the vibration unit. Thus, an optional timer is set to provide set time for a recalibration of the vibration source(s), and block  135  checks to see whether it is time to re-calibrate the unit. Block  140  responds to a triggering signal to trigger an avalanche by turning on the vibration source (and shaking the ground immediately around the vibration source). This triggering signal can result from sensing the amount of snow nearby, from a visual indication (an observer noting an accumulation of snow in the area) or from a remote signal (perhaps in response to a sensing of snowfall exceeding a preset limit or a time when the avalanche has been set to be triggered). 
         [0030]      FIG. 4  shows a representative plot the sensed ground vibration response (the output) as a function of the vibration frequency of the vibration source (the input). The sensors  40   a,    40   b,    40   c  and  40   d  shown in  FIG. 2  sense the effective ground vibration (or seismic activity) around the vibration source  30   a  as the frequency of the vibration is altered, then the vibration versus frequency is plotted. Each of these sensors (such as sensor  40   a ) may be an accelerometer or other suitable seismic sensing device with a suitable output or record. This frequency of vibration can be altered either manually (an operator changing the motor controls) or by an automatic stepping function, as desired. It is believed that  FIG. 4  shows a representative plot for a typical ground sample in an avalanche-prone area  20 . The plot  150  of operating frequency of the vibration source (along the x-axis) versus sensed vibration (along the y-axis) is shown in this view and includes a relative maximum  152  at f 1  (where the vibration level is v 1 ), an absolute maximum f 2  and another relative maximum f 3 . As shown in this  FIG. 4 , a vibration response or level v 1  is sensed at the frequency f 1 , the vibration response or level v 2  at the frequency f 2  and the vibration response or level v 3  at the frequency f 3 , with the vibration response or level v 2  being the highest of those shown in this  FIG. 4 . Under these circumstances, the frequency f 2  is chosen as the frequency where the greatest vibration is transmitted through this particular ground configuration. 
         [0031]    Of course, it may be easier (and more convenient as well as safer) to measure the ground response during periods of dry weather during a time when snow is not present—which would be a time when avalanches are not expected because there&#39;s no snow present and the temperatures might be warmer than those during the peak avalanche seasons. It is expected that the ground may have a different response to vibration based on temperature and based on the presence of (or absence of) a pile of snow, and the frequency at which the ground is most responsive may require adjustment for changes in temperature and ground loading. That is, the peak response may shift as a result of the ground becoming colder and/or piled with snow, and it may be desirable to compensate for changes in such variables in setting the preferred rate of vibration. It is also anticipated that different ground characteristics, even in adjacent areas, may produce different ground characteristics, requiring different frequencies to be used for different vibration sources, even though the sources may be close to one another. Accordingly, it will be apparent that the desirable operating frequency may be the observed best frequency with an offset to compensate for the temperature and for the snow pack on the ground in some instances. 
         [0032]      FIG. 5  is a cut-away side view of one vibration unit  30  useful in the present invention mounted within an aperture in the surrounding ground  300 . The vibration unit  30  includes a housing  210  to which legs  220  mount a flywheel  230  using bearings  240 . Drive belt  250  couples the flywheel  230  to a motor  260  which is mounted to the housing  210  by mounts  270 . An optional tension device  255  keeps the drive belt  250  taut. The motor  260  may generate heat and the assembly may be mounted in a location where the temperature varies depending on the time of year, so the belt  250  may need tightening over time or use, hence a tension device  255  may be provided—and periodic replacement and/or adjustment of the drive belt  250  may be desirable. 
         [0033]    The flywheel  230  is desirably asymmetric to produce vibration as it rotates. One way to achieve such asymmetry is to remove circular portions  230 ′ from one side of of the flywheel  230 , making the side of the flywheel  230  with the removed material lighter than the side of the flywheel  230  on which no material has been removed. Another way to create asymmetry (or unbalance) in the flywheel  230  would be to mount weights on one side, making that side of the flywheel heavier than the side without the weights. Yet another way to create an asymmetric flywheel is to mount the flywheel  230  off center, so that one side of the flywheel is heavier than the other side. 
         [0034]    The motor  260  may be a direct current motor operating at a relatively low voltage, such as 24 volts. A 24 volt power supply can be obtained through the use of two pair of 12 volt automotive batteries (or by other suitable powering, such as wiring into a commercial electrical supply or through the use of photovoltaic cells deriving power from solar energy which is then stored in batteries to be used when the sun is not shining). The motor  260  is one which can be driven at various speeds so that the optimum speed can be determined during a set-up or calibration period. That is, the motor  260  is operated at a range of different frequencies f 1 , f 2 , f 3 , . . . and the response of the ground in the vicinity is measured to determine which frequency provides the best transmission of vibrational forces (as discussed above in connection with  FIG. 4 ). That is, the ground  300  may have a differing response to vibrational forces at different frequencies, due to local differences in the materials and/or the adhesiveness of the ground in the vicinity. If the ground is very colluvial, it may be less transmissive of forces, including vibrational forces, than if the ground is more solid like granite, and the peak transmissive force is likely to occur at a different operating frequency. It is desirable in this application to determine the frequency at which the best transmission of vibrational forces occurs for each vibrational source at the location where it is situated and then, if necessary, adjust for variations in temperature and loading to determine the operating frequency for a controlled avalanche causing vibration and to induce the avalanche at a controlled time. 
         [0035]    The vibrational unit  30  has the housing  210  which may be a concrete culvert formed with a base which is either integral with it or securely attached to it. A steel plate  200  may be provided to securely mount the legs  220  and the motor  260  along with other components such as a battery and electrical conduit. The electrical conduit may serve the functions of signal transmission (to report the operating frequency, to set an operating frequency or to provide a signal triggering an avalanche) and may also serve as a power transmission function, either for providing primary power (providing the main drive for the motor driving the flywheel) or for providing back-up power (to supplement the power stored in a battery and/or generated by the photovoltaic cells). 
         [0036]    The top or upper portion of the vibration unit  30  is shown mounted approximately flush with the surrounding ground  300 . A cover  295  is shown atop the vibration unit to keep undesirable materials—soil and water (such as snow) from filling the vibration unit  30 . In addition, the lower portion of the housing  210  is provided with drain holes  290  to allow any water which enters the vibration unit  30  to drain from the vibration unit instead of accumulating and interfering with the operation of the components, including the flywheel  230 , motor  260  and the included electrical system and components. Additional apertures (not shown) may also be provided to allow electrical conduits to enter the vibration unit, but such apertures would often be positioned above the bottom of the vibration unit  30  to minimize water problems. 
         [0037]    The process of installing a vibration unit  30  in the ground  300  generally includes the step of preparing an aperture in the ground  300  slightly larger than the cross sectional shape of the vibrational unit  30  and approximately as deep as the height of the vibration unit  30 . Then the vibration unit  30  is inserted into the aperture. If there is clearance between the vibration unit  30  and the ground  300 , that clearance can be removed by filling the clearance with a suitable adhesive material, such as cement, shown by the reference numeral  292  between the ground  300  and the vibration unit  30  in  FIG. 5 . This adhesive material  292  provides the advantages of securing the vibration unit in place (so the vibration unit  30  less like to become dislodged, even in the event of an avalanche or water flow in the area) and to improve the force-transmission characteristics from the vibration unit  30  to the ground  300 . The adhesive material  292  also can serve a sealing function, to keep water from accumulating within the aperture. While the vibration unit  30  does not have to be cylindrical in shape, it is shown as such in this example to allow for a circular hole to be used as the aperture in the ground  300 . The circular shape also facilities use of a concrete culvert to be used in the present invention, with such devices being readily available and at a relatively low cost, since they are mass produced and widely used in other applications. 
         [0038]      FIG. 6  shows a top view of the vibration unit  30  used in the present invention (with the top removed to view the contents). This view suggests the cylindrical shape of the vibration unit  30  in its preferred embodiment, given the round cross section of the wall or housing  210 . Within the wall  210  are the motor  260  with the drive belt  250  and tension device  255  coupled to the belt  250 , with the drive belt  250  transmitting rotational force from the motor  260  to the flywheel  230 . The flywheel  230  is mounted by its legs  220  to the base  200  and bearings  240  are mounted to the flywheel  230 . 
         [0039]    Also shown in  FIG. 6  is a battery (or power supply)  410  which consists of two automotive 12 volt batteries connected in series to provide approximately 24 volts. The voltage for the batteries and their power type are chosen based on the requirements of the motor  260 , which in this case has been chosen as a 24 volt direct current motor. Of course, other types of motors  260  could be used to advantage in the present invention, and one might even use an alternating current motor if alternating current was available, either through a connection to a commercial power grid or through the use of an inverter, converting direct current into alternating current. 
         [0040]    Of course, many modifications are possible to the present invention without departing from its spirit and some of the features described can be used to advantage without the corresponding use of other features. While a preferred material of concrete has been discussed in connection with the foregoing example, there are many substitutes which could be used to advantage, including metals and alloys, if desired, including a steel housing (like a steel culvert). Some plastics may also be usable in the present invention. While the housing which has the vibratory source mounted can be a single piece, it also could be formed of multiple pieces which are secured together. Further, those skilled in the relevant art will appreciate that the present invention can be operable without being at its greatest effectiveness. For example, the tuning of the present invention will disclose the responsiveness of the soil to the vibrational forces applied, and it is possible to use an effective frequency without using the optimum frequency. It is also suggested that the system be re-tuned at periodic intervals, such as annually, to compensate for changes in the soil and/or attachment or changes in the operating characteristics of the vibrational source. It may be possible to predict the changes and adjust for the suspected changes in the operational characteristics without redoing the testing. Accordingly, it will be appreciated that the description of the preferred embodiment is for the purpose of illustrating the principles of the present invention and not in limitation thereof.