Research On Key Technology For Road Application Of Weathered Rock Aggregates In Typical Regions Of Shandong Province

The highway in Shandong Province is still under large-scale construction in the next five years,the potential demand for soil,stone and other resources is huge,while on the other hand,due to the rigid constraints of arable land,mountain protection and other policies,it is urgent to seek alternative road construction material resources.Some areas in Shandong Province are rich in weathered rock,and using weathered rock around the highway as road base and subgrade materials is a feasible solution for road construction material expansion.However,due to the large variability of the regional characteristics of weathered rock,some of the existing conclusions cannot be replicated.There is still a need for in-depth and systematic research on the key technologies,such as the determination method and reasonable value of the subarade resilience modulus of weathered rock,the strength characteristics and optimal stabilization scheme of different weathered rock used as sub-base materials,and the optimal gradation design and performance of the cement stabilized weathered rock used as base materials.Firstly,based on the "14th Five-Year Plan for Comprehensive Transportation Development in Shandong Province" and the topographic map of Shandong Province,the typical areas(JiNan,LaiWu,LinYi,WeiHai and YanTai)were selected for field research and sampling of weathered rock,and five types of weathered rock(corresponding to the above five areas,denoted by A,B,C,D and E)were sampled.The basic engineering characteristics were evaluated,and a resource base of weathered rock s for highways in Shandong Province was established.Secondly,the resilience modulus test and evaluation of different scales of weathered rock were carried out,and the prediction equation between indoor resilience modulus on water content and compaction degree was established,and the correction coefficient of indoor test results based on the field resilience modulus test method was proposed.The study shows that:the highest resilience modulus level of indoor weathered rock A is about 219 MPa;the modulus levels of B,C and D do not differ much and are at 115-125 MPa,and weathered rock E could not determined by the indoor test method due to the large super-grain size content;the resilience modulus has a non-linear relationship with water content and compaction,and the modulus values of actual water content and compaction can be predicted by using the equation;The modulus level obtained from the indoor model test is closer to the field test results,but the compaction forming and testing process is more tedious;taking weathered rock A as an example,the correction coefficient of resilience modulus of the indoor test based on the field test is about 0.55,and the main reason for the difference between the two is caused by the different size effect,surrounding pressure,loading level and force range of the tested soil.Then,the strength characteristics of three cement-stabilized weathered rocks(A,C and E)for subbase were carried out by indoor tests.The results showed that:when the cement dose is 3%,the compressive strength is ranked:E>C>A;when the cement dose is 4%and 5%,the average compressive strength is ranked:C>E>A.The compressive strength of all three types of weathered rocks increased with the increase of cement dose,but the strength growth rate was different.Based on the strength standard of highway subbase,the recommended cement dose for weathered rock A stabilization was 5%,and that for weathered rock C and E was 4%.The strength of cement-stabilized weathered rock is not only related to the gradation of weathered rock(5 mm particle size content),but also has an important relationship with the uniformity of cement dispersion in weathered rock,which is different from the variation law of resilience modulus of weathered rock.Finally,the key technology research of weathered rock applied to cement-stabilized gravel base was carried out.Based on the previous research of the group,the dense skeleton type compound grading design method based on the VCA was proposed,and the analytical expression of the amount of weathered rock and the grading optimization design process were given.The application and validation of the grading design method were carried out with the weathered rock A as an example,and the testing and analysis of the volume parameters,compressive strength,tensile strength and drying shrinkage properties were carried out for the cement-stabilized weathered rock filled with gravel with the optimized grading curve(called dense skeleton compact type)and the compared upper and lower grading curves(called control grading 3 and grading 4).The test results were as follows:according to the VCA of the compacted specimens:dense skeleton type<grade 4<grade 3;according to the 7d unconfined compressive strength:dense skeleton type>grade 4>grade 3,and the strength of dense skeleton compound reached the strength standard of highway subgrade;the splitting strength was ranked:grade 4>dense skeleton type>grade 2;the shrinkage coefficient was ranked:grade 3<dense skeleton type<grade 4.The study showed that the cement-stabilized weathered gravel filled with gravel of skeleton dense type had the smallest VCA,the largest compressive strength and larger tensile strength,and smaller dry shrinkage performance,which verified the rationality of the grading optimization design method and the feasibility of weathered gravel for highway subgrade.