They could, technically. Of course, there are various factors involved, most importantly the force of impact and the type of material. Since I see that you're working on a fantasy novel, and the character is wearing a tunic, I assume that the clothes aren't polyester.
Are they wool, cotton, linen? Does your character wear layers - linen undershirt beneath a woolen tunic, for example? How tight is the weave, and how thick is the fabric? A tighter weave is pierced less readily. Depending on economic status, the tunic would be of rougher or finer material - and rough, heavy wool will probably protect better than a light tunic of linen. I know it seems like a pain in the bottom to think about all this, but if you're concerned with realism, it does matter. (Anyone who knows more about fabric properties etc., please correct me if I'm wrong!)
If the forearms are likely to hit the pylon, or piling, or whatever the devil it is, I'm guessing that the character is striking from the front. Their forearms, if they have the chance to use them defensively, will absorb the brunt of the damage/shell fragments/what-have-you. Following that will be the face, and then the chest. If the arms are flung up to defend the face, then the chest will probably end up scraping against the shells quite a bit, though not nearly as much as the arms. (This is all just from my experience, and of course it depends on how your character reacts/is positioned upon impact.)
Don't forget that anything that passes through fabric to pierce skin will drag fibres into the flesh beneath. These can cause itching, irritation, infection, etc.
Also, consider subtler injuries such as torn/jarred muscles; bruising; breathlessness (from the impact driving the breath out of them); disorientation; swallowed/inhaled water, etc.
I feel like I'm rambling now, so I'll stop here.