Study On The Physical Mechanical Property Of Tunnel Debris Stabilized By Cement And Its Depth As Road Base

This paper takes Lingbao-Lushi section of Sanmenxia-Xichuan highway as the researchtarget, and conducts laboratory and onsite experiments on the tunnel debris excavated duringthe construction and the most appropriate depth of the road base composed of the tunneldebris.After selecting the re-crushed tunnel debris onsite, the author first conducts gradinganalysis and density tests towards the tunnel debris in the laboratory to have a comprehensiveunderstanding of its physical features and then determines four kinds of gradations of thetunnel debris according to the design codes through trial method based on the data derivedfrom the tests done above. Then the tunnel debris is mixed with cement, the weight of whichis respectively3%,4%,5%and6%of the total mixture. Compaction test is made afterwardsand finds that the maximum dry density and optimum moisture content occur when thecement accounts for4%of the total weight. Then7d unconfined compression test is given tothe four kinds of gradations mixed respectively with3%,4%,5%and6%of cement, whichdiscovers that gradation one and two are in conformity with the design specifications. The twokinds of gradations are then given14d and28d unconfined compression test, cleavage test,indoor compressive rebound modulus test, dry shrinkage test, temperature shrinkage test,flexural-tensile strength test and freeze-thaw test. Based on those tests above, it is concludedthat gradation two mixed with4%cement can meet the criteria to serve as the base forhigh-grade highways.The author then conducts rebound modulus test and deflection flexure test on therock-fill road embankment and earth-fill road embankment, and calculates the base designparameters according to the data derived from gradation two mixed with4%cement and thefeasibility study report, and recommends the depth of the road base to be220mm aftercalculating and verifying the base depth via HPSD2006and Bisar3.0.The author then chooses100m of rock-filled road embankment as the trial lot and lays abase of220mm as recommended. On the four cross-sections within the trial lot, the straincapacity and temperature changes of the base and sub-base are measured by the strain gauges beneath them. In the meantime, strain gauges are also buried under the rock-filled roadembankment and earth-filled road embankment of the existing highway to get thecorresponding figures of the strain capacity and temperature changes. After the comparison ismade between the two sets of figures, it is finally proved that the base of220mm meets therequirement after converting the figures derived from the trial lot into stress.The findings of this study will provide reference to the utilization of tunnel debris in theroad project in the mountain area and the depth design of the base laid with tunnel debrisstabilized by cement.