INPUT ARTICLE: Article: In a broad sense, "sin" refers to anything that falls short of the holiness of God. The easiest to spot are usually actions, but sins can also include thoughts and attitudes. Certain actions are considered sins, but the desire to perform those actions is sinful, as well. For instance, wanting to commit adultery is a sin just as actually committing adultery is. Temptation is not a sin, though. If you're put in a compromising situation with someone you find physically attractive, you may feel tempted to act on that attraction. Actually acting on that attraction and committing adultery as a result, or imagining the act of committing adultery even without doing it, is the sin. Simply feeling tempted to do so is not. Even though mankind was created in the image of God, the fall of Adam and Evethe first humanssignified the fall of all humanity. As a result, humans are sinful by their very nature. In other words, you don't have to be taught how to sin. Sin is already firmly fixed inside of you at the very core of your being from the time of your birth. When Jesus died on the cross, He carried the sins of humanity with Him. Christ's sacrifice canceled out the debt of original sin. In the Old Testament, animal sacrifices were used as a way to repent for the sins of flesh. Even these sacrifices were imperfect, though, so the stain of original sin still remained. As both Son of God and Son of Man, Jesus became the "perfect sacrifice," capable of freeing the human soul from the chains and punishment of original sin. " Accepting Christ and being freed from sin does not mean that you will never do another wicked thing ever again. Christ's sacrifice freed your spirit from the shackles of sin. Your fleshincluding your body, mind, and heartwill still have to deal with everyday sin. Your soul can be free from sin even though your body still sins. Being free from sin on a soul level should mean that you also seek freedom from sin on a physical level, though, even though it can never be permanently reached.

SUMMARY: Define sin. Accept the sinful nature of humanity. Understand the significance of Christ's sacrifice. Know what it means to be "free from sin.

INPUT ARTICLE: Article: Tunnel boring machines, called TBMs for short or "moles," feature circular plates on the front called shields. Disc-shaped cutters on the shield tear through rock and dirt, which passes through openings in the shield onto a conveyor belt inside the TBM that deposit it behind the machine. The types of TBM shields vary according to whether the mole is to dig into soft, wet ground or hard rock. Shield diameters range from Aker Wirth's 26.3-foot (8.03 m) shield on its TBM used for Switzerland's Linth-Limmern power stations to Hitachi Zosen's "Big Bertha," with its diameter of 57.5 feet (17.5 m). Moles designed to dig tunnels below the water table also feature chambers at the front to pressurize the ground being dug through. For large jobs, multiple TBMs may be called for. The Channel Tunnel required 11. For a surface level tunnel, this is no problem. If the tunnel is to be bored deep underground, an access shaft, usually circular, is drilled and lined with concrete. The TBM is lowered into it, and the tunnel is excavated from that point. For long tunnels, multiple access shafts are drilled. When the tunnel is finished, the access shafts may become ventilation shafts and/or emergency exits. If they are not so employed, they are left in place for the life of the tunnel. Segments of pre-cast concrete are erected behind the TBM to form a ring at pre-determined intervals. The sprayed concrete, or shotcrete, coats and stabilizes the tunnel walls. The shotcrete may include steel or polypropylene fibers to strengthen it, much the way steel rebar is used to strengthen cast concrete. The shotcrete also contains an accelerant to help it stick to the tunnel walls and dry quickly.

SUMMARY:
Choose the right tunneling machine for the job. Get the machine into position. Erect tunnel supports as the machine bores through. Spray concrete on the excavated walls between the support rings.