Which of the following is true when blasting underground?

When blasting underground, it is crucial to consider the relationship between the force of the blast and the surrounding material's resistance. The correct statement reflects that in underground blasting scenarios, the resistance offered by the surrounding earth and rock typically absorbs some of the blast force. This absorption limits displacement and helps control fractures and potential fly rock.

Understanding this dynamic is essential for safety and efficiency in underground operations. If the blast force were greater than the resistance, it could lead to uncontrolled fracturing, excessive vibrations, or even structural damage to the surrounding environment. Therefore, recognizing that the force of the blast is indeed less than the resistance ensures that controlled outcomes are achieved, which is a fundamental principle in the practice of effective blasting.

The other statements do not align with the principles of underground blasting. Ignoring the resistance's impact on blast forces can lead to unsafe conditions and ineffective blasting results.