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Investigation into Continued Damage at the Solitario Ranch Page 9 <br />i <br />1 <br />One aspect of the analysis of the damage to the house by Mr. Attwooll and Mr. <br />Reins, and discussed verbally, was that the house might have been raised to <br />cause the damage, instead of settling, this potential phenomenon was observed by <br />investigators in a similar situation where pillars had punched into the soft mine <br />floor. And had caused a "heave zone" at the edges of the surface expression of <br />subsidence.13 <br />The type of ground movement in this type of pillar failure is relatively gradual <br />and not abrupt, as with a long wall subsidence situation. It does not always <br />produce cracks on the surface especially if there was heaving involved. The <br />cracks, as they might appear, would heal with the flow of the soils on the surface. <br />There were cracks on the surface over the 18` Left entry (NW#1) as it subsided, <br />noted by personal observation, conversations with Basin Employees and the <br />Rancho Escondido Project Manager, subsidence in this area was up to 7 ft. <br />according to some reports, but they have all healed and are not easily visible at <br />this time. <br />New Studies <br />The input to the SDPS program was revised to consider continued failure of <br />pillars adjacent to those predicted in the analysis done in 1996. The SDPS <br />software has been updated and a new version has been purchased and the <br />analysis indicates that a relatively small change in pillar integrity will influence <br />the surface at the house18. <br />The data sheets for the mine plans used for the calculations are attached as <br />Exhibits; Exhibit 1 represents the basic assumptions that were used to calculate <br />the subsidence curves in 1996. It has been upgraded to SDPS ver. 5.1. Exhibit 2 <br />is the revised mine plan that indicates that continued weakness in the mine floor <br />will continue to affect the house. Figure 1 is a sketch map that shows the panels, <br />the prediction points, survey stations, and the Tatum house. Figure 2 is a curve <br />showing the SU's and distances produced from the SDPS program. Figure 3 <br />shows the same data except with more clarity. <br />The Parameters, Tang and B, were developed during the process of matching the <br />actual subsidence curves to the computed curves. Tan B is the tangent of the <br />influence angle, and B, is the empirical strain coefficient, 0.35 is the default <br />value. The prediction points for these models were laid out on a grid that <br />approximated the location of the survey monuments 1N-1 and 1N-2 and running <br />in a north-south direction. Surface elevations were estimated from a topographic <br />map. <br />Three mine parcels were used for this study; there is an option of using as many <br />parcels as there are pillars in the mine, or even more. Using fewer parcels <br />reduces computation time and experience has shown that the computed values <br />are nearly equal. The data for the parcels, coordinates and elevations, were <br />obtained from the underground survey notes obtained from Basin for the trial. <br />Seam thickness was estimated and the subsidence factor was calculated by trial <br />and error from the actual subsidence cases in the area. Where the pillars had <br />failed, a subsidence factor of 68 was used, the factor for partial failure was <br />adjusted downward, and for no failure the factor is 5. <br />When a pillar fails by punching into the mine floor, the material from the floor <br />expands to fill the mine entries around the pillars. The maximum amount of <br />is Various worksheets and maps included in Appendix 9 <br />