{"id":3132,"date":"2026-01-30T10:00:21","date_gmt":"2026-01-30T02:00:21","guid":{"rendered":"https:\/\/www.zongdamining.com\/?p=3132"},"modified":"2026-01-27T12:01:46","modified_gmt":"2026-01-27T04:01:46","slug":"how-to-match-underground-mining-transport-vehicles-for-efficiency-the-3-pass-rule-explained","status":"publish","type":"post","link":"https:\/\/www.zongdamining.com\/fr\/how-to-match-underground-mining-transport-vehicles-for-efficiency-the-3-pass-rule-explained\/","title":{"rendered":"How to Match Underground Mining Transport Vehicles for Efficiency: The 3-Pass Rule Explained"},"content":{"rendered":"
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The “Hidden” Bottleneck in Your Haulage System<\/strong><\/h2>\n

In the quest for higher tonnage, the instinct of many mine managers is simply to buy more iron. The logic seems sound enough: adding more underground mining transport vehicles<\/strong><\/a> to the fleet should result in more ore moving up the decline, right?<\/p>\n

Not necessarily. In fact, adding capacity without calculating the Match Factor is often the fastest way to burn capital without seeing a return. You might notice the queue at the loading point getting longer, while the crusher sits empty.<\/p>\n

According to recent simulation studies on underground mine haulage, incorrectly scaling a fleet can lead to a “utilization cliff.” The data reveals that simply throwing trucks at a haulage system in underground mining without balancing the loader capacity causes vehicle utilization to drop significantly. The culprit is queuing.<\/p>\n

Optimization isn’t about buying the biggest machines; it is about creating a balanced flow. This article explains the science behind the “3-Pass Rule” and how to apply it to your fleet to stop wasting fuel on idling engines.<\/p>\n

The Science Behind the Match: What the Data Says<\/strong><\/h3>\n

Before getting to the rule of thumb, it is crucial to look at the engineering reality. The efficiency of a load-haul-dump (LHD) cycle is dictated entirely by the interaction between the loader’s bucket and the truck’s box. It is a relationship that does not forgive bad math.<\/p>\n

Recent research modeled the impact of increasing truck numbers in a single-loader stope operation, and the results were stark.<\/p>\n

The Utilization Drop<\/strong><\/h3>\n

When the number of trucks increased from two to three in the simulation, the average truck utilization rate plummeted from 97% to 75%. That is a massive hit. You are paying for 100% of a machine but only using three-quarters of it.<\/p>\n

The Queue Trap<\/strong><\/h3>\n

The study identified “Queuing Time” as the primary efficiency killer. With too many trucks serving one loader, the expensive haulage units spent significant time idling. This is the “Queue Trap.” In certain scenarios, adding a fourth truck reduced the total task completion time by a negligible amount\u2014from 769 minutes down to just 762 minutes. You effectively pay for a whole new machine just to save seven minutes per shift.<\/p>\n

The “3-Pass Rule”: The Golden Ratio<\/strong><\/h2>\n

To avoid this trap, veteran mining engineers rely on the 3-Pass Rule. It is a simple, field-proven metric to size underground mining transport vehicles correctly.<\/p>\n

Why 3 to 4 Passes?<\/strong><\/h3>\n

This rule states that, ideally, the LHD loader should fill the mining truck in 3 to 4 passes (buckets).<\/p>\n

If the cycle is under 3 passes (say, 2 buckets), the loader is too big for the truck. You risk “shock loading,” which destroys the truck’s suspension and tires over time, and spillage over the sides becomes highly likely.<\/p>\n

If the cycle is over 5 passes, the truck sits idle for too long while the loader scrambles back and forth. The truck driver is just sitting there burning diesel, and the truck\u2019s tons-per-hour (TPH) potential is destroyed. Achieving a 3-4 pass match synchronizes the loader cycle with the truck cycle, ensuring a continuous flow of rock.<\/p>\n

Applying the Rule: Real-World Configurations<\/strong><\/h3>\n

To see how this theory applies to actual operations, the following examples demonstrate the math using standard equipment specifications. These configurations show how matching the right ZDL series loader with the correct truck capacity creates an efficient loop.<\/p>\n

Scenario A: Narrow Vein Precision (2.5m Tunnels)<\/strong><\/h2>\n

For tight operations where clearance is king, a common mistake is pairing a tiny scooptram with a truck that is just slightly too big, killing cycle times. Let\u2019s calculate the match for a compact fleet:<\/p>\n