【導(dǎo)讀】為準(zhǔn)。sametime.toasbaselayer.classes.arealsoprovided.

　　

【正文】 rmula ()Z: )1/( vad CZRR ??? () where, Rd – designed pression strength (Table )。 Cv – Coefficient of deviation of the test result (as decimal fraction)。 Za – coefficient that varies with the factor of assurance (or confidence α ) in the normal distribution plot. Speedway and firstclass highway shall take the factor of assurance as 95%, and in this case Za=。 ordinary highway shall take the factor of assurance as 90%, and in this case Za=. The actual dosage adopted at the worksite shall be %~% more than that identified by the indoor test. When the centralized shop mixing method is adopted, only % addition is permitted。 when the road mixing method is adopted, the addition should be 1%. The minimal dosage of cement shall be in pliance with Table ~3. Table Minimal dosage of cement Mixing method Clay type Road mixing Centralized (shop) mixing Medium and coarsegrained clay 4% 3% Finegrained clay 5% 4% The position design for bined stabilized clay shall have the same steps as above. 14/151 Roadmixing Construction The flow chart for the road mixing method shall be in the sequence shown in Fig. . Preparing lower bearing layer → Construction plotting → Crushing clay or transferring and spreading aggregates → Spraying water for wetting → Flattening and slightly pressing → Placing and spreading cement → Blending (dry blending) → Adding water and wet mixing → Forming → Rolling → Treatment of joints and turning points → Curing Fig. Flow chart for clay cement Preparing lower bearing layer The lower bearing layer of clay cement shall be smooth and solid, with road crown as specified, and without any loose material or weak point. The smoothness and pactness of the lower bearing layer shall be in pliance with Section of this Code. When clay cement is used as base layer, a subbase shall be prepared。 when clay cement is used as reinforcing layer of old road surface, the old road surface shall be prepared。 when clay cement is used as subbase, clay base shall be prepared. (1) Clay base must be subject to rolling inspection (rolling 3~4 times) with 12~15t threewheel road roller or equivalent rolling machine, whether it is embankment or road cutting. During the rolling, in case of any overdry or surface looseness identified, a proper amount of water shall be sprayed. In case the clay is so wet as to cause spongy clay, measures shall be taken for treatment, such as digging out for sun drying, clay replacement, blending with lime or cement, etc. (2) Subbase layer shall be subject to pactness test。 flexible subbase shall also be subject to deflection value testing. For road sections not in pliance with the design requirement, measures must be taken respectively according to the specific situation, including rolling, replacement with better material, digging out for sun drying etc so that they can reach the specified standard. (3) Low places and pits on the subbase of old road surface shall be carefully filled up and pacted。 corrugation and wheel rut shall be scraped off。 loose points shall be harrowed, water sprayed and rerolled to reach smoothness and pactness. 15/151 (4) Newly pleted subbase or clay base must be subject to acceptance inspection as specified in section of this Code. For any road section that has failed the acceptance, measures must be taken to allow it to reach the standard before clay cement layer can be spread and laid. (5) It is required to check the elevations of the lower bearing layer cross section by cross section to make sure they are in pliance with the design requirement. The error of elevation of the lower bearing layer shall be in pliance with Section of this Code. On trough shaped road sections, relief ditches (or blind ditches) shall be made on both road shoulders at certain spacing (., 5~10m) in staggered arrangement. Construction Plotting (1) Restore the middle line on the subbase or old road surface or clay base. Set a pile every 15~20m along straight line sections, or every 10~15m along horizontal curved sections, and set indicating piles on the outside edge of the road shoulders on both sides. (2) Make level survey. On the indicating piles on both sides, mark with conspicuous signs the design height of the edge of clay cement layer. Material Preparation Make use of materials on top of old road surface or clay base (1) Foreign matters such as stones on the surface of the old road or clay base shall be first removed. (2) Dig a hole every 10~20m and make sure the hole bottom elevation is the sane as the expected bottom surface elevation of the clay cement layer. Lease a mark at the bottom of the hole to control the depth of scarification and crushing. (3) Make sure the top of the old road surface or clay base has reached the predefined depth of scarification by means of plow, ripper, or grader or bulldozer with reinforced teeth. Clay clods must be crushed to meet the requirement. (4) It is required to frequently turn the clay from both sides to the center with a plow so that the sides of the layer for scheduled treatment form a perpendicular plane, thus preventing the width of treatment from exceeding the stipulation. (5) Crush clayey clay with special purpose machinery. Where no special purpose machinery is available, the gyrotilling machine or disk harrow can be used to crush clay with small plasticity index. 16/151 Make use of the aggregates in the stock yard (1) Prior to collection of aggregates, first remove wood/trees, turf and irrelevant earth. (2) Oversize grains shall be screened out of