Study On The Soft Rock Engineering Characteristic Of Ji-Hun Freeway Along The Line

In recent years, Jilin to Hunchun highway and nearby cutting has been a number of cases of small and middle slope instability, and brings to the construction a lot of difficulties. Dunhua to Yanji freeway which is about to construct in Taiwan mountain No.2, No.3 Pass , Chaoyang Town, Longjing City and the viaduct excavation segment both have creep signs. So, Jilin Provincial Communications Department commissioned Highway Survey and Design Institute of Jilin Province to conduct special research for it. In April 2001, a program called "Study on the slope stability appraisal and reinforcing method of Jilin to Hunchun Freeway " started on .This article is based on the studies above, aims at the expansive soft rock engineering properties and soft rock slope and the related problems to do a large number of experimental and theoretical researches.This article takes the soft rock engineering properties in Jilin to Hunchun highway and the stability analysis on the cutting slope as issue. From the geological conditions survey research, and launch a series of soft rock characteristics. On the basis of deep investigation on the geological conditions in Hunchun to Jilin expressway, fix on sampling location, base on different properties of the soft rock, develop a number of trial studies. Focus on the hydraulic characteristics and mechanical properties of typical soft-rock group in the Taiyan mountain, No.2, No.3 Pass and the hydraulic characteristics in the viaduct excavation segment and other soft rock distribution.X-ray diffraction analysis of the profile of the rock group structure construction, mineral composition, Components of a comprehensive system of identification analysis. Rock composition and microscopic structure identification, to some extentfrom the micro appear soft rock rock the complex physical and mechanical properties of particularity. Through the collapse of experiments, : soft rock have strong properties with water rapidly disintegrating; Shallow soft rock collapse of a highly. Deep and soft rock (10.0m) in collapsed relatively weaker sex has collapsed with the depth increments regressive law; The collapse of a highly soft rock collapsed just a few minutes can be completed, Individual weaker collapse of the soft rock would require a few hours or several days to the occurrence of at-risk micro-fracture; With the bubble powder collapse of its main manifestations.Conducted a number of mechanical test, by creep experiments, we find that the long-term mechanical strength index of weathered mudstone in this area is low, the cohesive force C∞ranges from 9.8~14.0kPa, the mean value is 11.23kPa; internal friction angleΦ∞is between10.0°～13.5°, the mean value is 12.1°. Through triaxial compression experiments:①in the weathered mudstone natural state. its peak cohesion is between 21~68kPa (average 52.4kPa), internal friction angle between 3°to 9°(average 6.3°);②And weathered mudstone saturated peak cohesion is between the 21kPa~48kPa (an average of 35.7kPa), the internal friction angle is between 0°～4°;③in the saturation state of strong clayey siltstone triaxial shear tests, the peak cohesion is in 106kPa~150kPa, the internal friction angle is between 39°～44°. And through the direct shear experiment under natural saturation state, educe the soft rock in the region :①t he peak cohesion in natural state is between 15~68kPa, the internal friction angle is between 18°～38°;②t he peak cohesion in the saturated state is between 13kPa~63kPa ,the internal friction angle is between15°～30°;③the residual cohesion in natural state is between 14~38kPa, the internal friction angle is between 15°～30°;④the residual cohesion in saturation state is between 10kPa~25kPa, the internal friction angle is between 12°～29°. From variable water direct shear testresults can be obtained in the region of soft rock :①t he shear strength of soft rock changes with the water content;②With the decrease of water content, the shear strength is larger.③t he sensitive of weathered mudstone is bigger than weathered mudstone with changes in the water content. By uniaxial compression testing draw:①the uniaxial compressive strength of weathered mudstone in natural state is between 0.331~1.433MPa, the uniaxial compressive strength of the clayey siltstone is between 0.566~1.689MPa;②the elastic modulus of weathered mudstone in natural state is between 1.69~6.45GPa, the elastic modulus of strong weathered mudstone is between 3.47~7.22GPa;③in uniaxial compression process of strong clayey siltstone, the ultimate stress appears when the axial strain is between 1～2%.A lot of expansive testing results show: the free expansive rate of the weathered mudstone in the region generally ranges from 60%~110%. Mean value is 85.7%, the no load expansive rate ranges from 0.16%~4.48%. Even if the same depth of its soft rock samples, the no load expansive rate differential is great; at the vertical load stress more than 100kPa, the natural state of the soft rock a smaller rate, not more than 1.15%; natural state of the expansion value is from 7.1~49.1kPa the mean value is 24.82kPa.Cutting soft rock generally should be reasonably used for reclamation roadbed material, it needs to know the soft rock compaction and consolidation characteristics, So do compaction and CBR test on the soft rock near the Taiyan mountain. The soft rock of this segments mixed material of compaction optimal water content and the maximal dry density corresponding are 11.0%~17.4% and 1.75~1.97g/cm3. Give the consolidation curve and CBR curve.Finally, the article does preliminary study on calculation parameters when appraising the slope stability of expansive soft rock (the shear strength index C,?value of slope rock), the slope critical value when design slope, landslides and slope mechanism of control measures.By studying educe the conclusions as follows :1. Do trail study entirely and systemically on the expansive soft rock in the Yanbian region Jihui highway. And fill up expansive rock in the field of geotechnical study of the Yanbian region information.2. Find out the mainly cause of slope distorting destroy in Yanbian area is that Yanbian region contains large amounts of soft rock expansive clay. Point out the landslide-prone sensitivity stratum: the third Hunchun group (E2-3h) and the Cretaceous strata Longjing stratum (K2l).3. Selecting parameters of slope stability analysis, bring forward a method of selecting rock mechanics parameters which considering the stratigraphic position, and finally, fix on the rock slope mechanical parameters of key part of the soft rock excavation.4. Bring forward the critical slope and height of excavation slope in expansive soft rock highway section.