Research Of HSMR Fast Evaluation System For Stratiform Rock Slope Of High-Grade Highway In Mountain Area

Mountain high-grade highway construction have the following characteristics: longdistance and passing more geological landform region, short cycle from survey and design toconstruction. These make the subgrade engineering geology characteristic and problemdifficult to fully and deeply investigation. Above reason make the subgrade slope designpossess uncertainty and embed hidden trouble for the road engineering construction.Therefore, conventional slope stability investigation method is out of date, the new methodmust be found.The expressway slope of the national road 108 route Guangyuan Segment, Kunshi Road,Guanglin Road, Yulin Road and Yuqian Road in southwest mountain area have beenresearched. The slope structure types and stabiliy have been concluded and summarized, then,the stability evaluation of stratiform rock slopes have been taken as main research objectwhich is big quantity and high hazard. On the basis of collecting materials, deep and carefulanalysis about slope's forming environment, basic geological condition, structure types,deformation and breakage pattern and its mechanism was carried on, then using statistics andgeology engineering theory, the relative of rock slope stability and landform, slope elevation,slope angle, structure characteristic, lithology, lithology combination situation etc. have beenstudied. The stratiform rock slope mass rating which suit to high-grade highway has beenanalyzed and discussed.This system includes two levels, firstly, because of the geological data lack in mountainroad design phase, the author using rock structure and geological process mechanism analysismethods, established a concise rock slope stability criterion which mainly base of geologymacro judgment. Secondly, considering the construction phase have more geological data, onthe basis of Slope Mass Rating (SMR) and Chinese system for Slope Mass Rating (CSMR),the Highway rock Slope Mass Rating (HSMR) has been presented which suit to fastevaluation of rock slope stability in mountain. So the stability of excavated slope can be havefast and exact appraisal in road design and construction phase. The details are as follows: (1) To the road slope excavation characteristics, put forward and regard 45°as thedemarcation line which divides the rock stratum with steep, slow inclination, on this basis, aconcise rock slope stability criterion is established(table.1).By using the criterion, thestability of the rock slope along the line can be comparatively accurate judged in designphase, so the corresponding reinforcement and administration measure can be taken. Duringthe course of construction, because the materials are more abundant, more accurate fastjudgement to the rock slope stability can be made; thus put forward more pointedreinforcement scheme.(2) Because the common rock mass classified system is established on the basis ofwater-power engneering or mine engineering, which can not best be used in road rock slopestability evaluation, the normalization managed method has been introduced, which can makeeach system grade value difference visible, easy to do the difference analysis. Then, thecredibility degree conception has been introduced, which can do the correlation andconsistency analysis for the preliminary classified result, find out the relation and differenceof each classified system. These established the foundation of HSMR rate..(3) Though there is categorised system that has considered structural impact on the slopestability at present, there are some shortage. For example, its very difficult to accord with thestability of soft, hard rock slopes mutually. On the basis of fully considering structural indexof rock mass, lithology combination has been included in the hierarchical system ascommenting factor, which improved the marked accuracy of rock slope stability system.(4) The relation between the slope stability and its height is not simple linear relations.Considering the simple operation of categorised system, reject the complicated andsuperfluous physics mechanics parameter, then by using statistical analysis of a large numberof samples, Seeked a simple and convenient revision function about slope height, which cannarrow the difference of the categorised result of the original system and actual conditions as much as possible, and meet the preliminary appraisal requirement of stability.(5) 113 slopes have been taken as studied object, then, high-grade Highway stratiformrock Slope Mass Rating (HSMR) has been introduced: HSMR=ξRMR-ηλ(F₁×F₂×F3)+F₄HSMR value can be calculated according to the above formula, its maximum is 100, theminimum is 0. Regarding 20 as the interval, which is divided into 5 ranks (table.2):These system is best be used in geological data relatively abundance construction phaseor be used in older line reconstruction design phase. The "mistake judgment ratio"conception has been further introduced, systematically evaluated the HSMR applicationeffect, proved this system reliability.