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• -24- <br />It is our opinion that there are several factors or phenomenon <br />which are resisting failure of the spoil bank from a massive failure. <br />The fire clay we observed in our test pit was relatively thin (3 <br />inches) and discontinuous and may not be present in sufficient extent <br />to adversely affect or control mass stability. The relatively large <br />spoils near the bottom of the pit may have over time been "pushed" <br />through the soft material until contact is made with stronger materials <br />on the pit floor. This would result in an overall decline in the affect <br />of the clay layer and result in relatively high friction directly between <br />the bottom of the spoil and the pit floor. It is our opinion that a <br />combination of the above is occurring which results in the clay zone <br />not affecting overall mass stability. <br />f� J <br />rnn .-lucinnc <br />The results of our analysis indicate that the spoil bank isstable <br />from a massive failure standpoint at its current: configuration. Neglect- <br />ing failure surfaces which pass through the fire clay the lowest factor <br />of safety calculated was about 1.2 for a circular surface passing <br />entirely through the spoil. <br />Our analysis further indicates that while the bank isstable pre- <br />sently against massive failure, some shallow failures may occur in the <br />future. Since most of the slope faces are at their angles of respose, <br />the factor of safety for shallow failures is 1.0. This type of shallow <br />or sheet failure does not appear to have occurred at this time within <br />