A naturalistic substrate, even those including play sand, can be used for animals that burrow. Owners should, however, provide an area of tile, smooth rock, or carpet for offering food to help reduce the risk of accidental ingestion of the substrate (Wilkinson, 2015). It is best to provide softer substrates, rather than sharp wood chips, because it is possible for tortoises to be cut or irritated by sharply-edged substrate. Some like to use a mix of coconut coir and organic soils, which is a good option when a clay-y soil is chosen. Try out different brands of organic soils and you may find one that is not so muddy. Just check the ingredients and/or additives to be sure it is safe to use. Unsafe additives include perlite, slow release fertilizer pellets (however, this shouldn’t actually be in organic soils).
This website has great advice and info about different substrates if you want to read more: https://startortoises.net/substrates.html
References:
Wilkinson, S.L. (2015) Reptile Wellness Management. Vet Clin Exot Anim, 18: 281-304.