Shares in Shaft Sinkers Holdings tumbled after the company said full-year profits and revenues would be lower due to reduced workload and a weakening South African rand.
The deteriorating value of the rand against sterling affected revenues by some 11%, according to the shaft sinking and underground construction group's trading update on Monday.
The group's profitability will be "materially below expectations" for the year through December 2013. Profit before tax is expected to be between £2.5m and £3m.
Profits were also hurt by operational difficulties, which resulted in reduced billings to clients.
Gross margin is anticipated to have decreased to between 9% to 10% from 11.7% in 2012.
The company operations were negatively affected by poor sinking progress at the Hindustan Zinc project, which resulted in higher than expected costs and lower revenues.
The group experienced a "disappointing" performance at the Impala 17 and Styldrift projects in South Africa.
Union strikes continue to affect the group's operations for Impala Platinum Holdings and Lonmin.
The contract for the sinking of a new shaft for Kazchrome was also delayed with talks ongoing.
The project includes the sinking of the Skipovaya vertical shaft to access a chromite ore-body at the Donskoy mine and ore processing plant in the Aktujbinsk region, Kazakhstan.
Progress at the group's other projects, including the Kibali Goldmine project, Lonmin's Saffy, Hossy and Karee 3 projects, and Afplats' Leeuwkop project was broadly in-line with management's expectations.
Full-year operating expenses were reduced to about £17m from £23.7m.
Operating income for the year is expected to include a £1.6m gain from foreign exchange
movements and £0.9m profit on the sale of plant, property and equipment.
At the end of the period the group had gross cash of £4.1m, drawn overdraft of £3m and £2.9m of interest bearing term debt.
The order book stood at about £350m, up from £344.1m at the end of June.
Chief Executive, Alon Davidov, said: "The group has endured an extremely difficult trading period in South Africa and the labour concerns remain for the current year.
"We are disappointed by the performance of the HZL project during the final quarter of 2013, however management has reacted quickly to address the issues. Numerous cost reduction exercises have been implemented in order to ensure the business can sustain the lower gross profit and exceptional legal charges.
"Nonetheless, I am confident that the business has solid fundamentals to ensure its future profitability once these adverse factors have been resolved."
Shares fell 13.64% to 14.25p at 11:07 on Monday.