The least absolute deviation (LAD) method has some favorable properties

including intuitiveness

robustness

zero-error

predictability and generalization

compared to the least square (LS) method. The LAD approximation is a "mini-mini approximation"

which is minimization of the minimum absolute value of error. Because the best result of the mini-mini approximation must be zero

the zero-error principle is indeed the basic principle of LAD method. The realization of the LAD solution is achieved by a "representative" data processing mode. Because the disturbance induced by the data with big error is removed

the LAD method has a good robustness. Since the representative data are selected according to different applications

the LAD method is widely applicable. When the LAD method is applied to prediction

the endpoint data can be set to be zero-error data

yielding the unequal weights of the data which are closer to the end point. As a result

the endpoint data have the greatest weight

and have a basis without errors

making the proposed procedure more reasonable and more accurate. Based on three engineering cases

the LAD method is applied to predicting the settlement process of rock and soil foundation. By comparing with LS method

it is concluded that: 1) The stability of data processing of LDA method is better

the fluctuation range is smaller

and the forecasted result is more accurate; 2) Ccntradictory and unreasonable phenomenon no longer appear as in the data processing of LS method; 3) when t→∞

although the limit settlement values cannot be verified

the prediction of LAD method is more reasonable than those of LS method

since the LAD method is built on the basis without errors.