# Applicable Conditions of Room-and-Pillar Mining Goal Treatment Methods under a Traffic Load
###### Abstract  
The disturbance depth of traffic load has a direct impact on the stability of a room-and-pillar mining goal. To quantitatively calculate the relationship between the traffic load disturbance depth and influencing factors, 49 groups of horizontal combinations of different influencing parameters are designed in this study, based on the orthogonal experimental design method. Midas GTS is used to simulate and obtain the corresponding traffic load disturbance depth data. A multivariate linear regression analysis of the traffic load disturbance depth is conducted, and a regression formula for calculating the traffic load disturbance depth is established. According to the traffic load disturbance depth, goal depth, and the stability of the roof, coal pillar, and base plate under traffic load conditions, a judgment flow of the room-and-pillar mining goal treatment method under traffic load conditions is established, and it is applied to the reconstruction and expansion project of the Jixi section of the Dan-A national highway. The results show that a geogrid can be used for treatment purposes when the traffic load disturbance depth is 1.5 times lower than the depth of the room-and-pillar mining goal, or when the traffic load disturbance depth is 1.5 times greater than the depth of the room-and-pillar mining goal but the roof, coal pillar, and base plate are stable. Additionally, grouping is needed for treatment in other cases. The results of this study can provide a scientific basis for the selection of treatment methods for room-and-pillar mining goals underlying highways in the future. The results are of great significance in the field of engineering for the safety measures concerning highway room-and-pillar mining goals. traffic load; room-and-pillar mining goal; goal treatment; orthogonal test +
Footnote †: journal: Medical  
characteristics that signify their instability and failure [5], their pressure relief properties [6], the evaluation method used for coal-pillar stability assessments [7], and the calculation formula used for coal-pillar strength assessments [8]. In relation to the issue of the roof, research has been conducted on the influencing factors of roof stability [9], including the safe thickness property of a roof [10] and the total span of the roof [11], as well as other issues. Some scholars have also evaluated the coupling of a coal pillar and roof [12]. The research that has been conducted on the issue of traffic load include the law of transmission and the diffusion of the traffic load [13], the effect of the model of the vehicle load [14], the dynamic response of soil under traffic load conditions [15], and road subsidence under heavy traffic load conditions [16]. For roads built on goat areas, grouting is often used in engineering practices to treat these goat areas to avoid the hidden dangers of road construction and operation, such as surface subsidence and roadbed collapse, caused by the sudden instability of the goat areas [17; 18; 19; 20; 21]. Although this form of treatment can solve the above-mentioned hidden dangers, it also leads to a substantial increase in construction costs. With the expansion of research in this area, some scholars have proposed that when a coal pillar and a roof in goofs are stable under traffic load conditions, it is then only necessary to lay a geogrid on the subgrade for treatment without using grouting to fill the goat [22]. Thus, the key to the treatment of a subgrade with a geogrid is to determine the stability of the coal pillar and roof in the goat under the traffic load. However, the method of evaluating the coal pillar and roof stability in the goaf under the traffic load--although it was involved in the previous research--is not perfect or universal (such as simplifying the traffic load to a static load without considering the influence of the dynamic vehicle load, or using the disturbance depth relative to the mining depth as a judgment method in which the bearing capacity of the coal pillar and roof are not considered).