AbstractIf $U:[0,+\infty [\times M$
U
:
[
0
,
+
∞
[
×
M
is a uniformly continuous viscosity solution of the evolution Hamilton-Jacobi equation $$ \partial _{t}U+ H(x,\partial _{x}U)=0, $$
∂
t
U
+
H
(
x
,
∂
x
U
)
=
0
,
where $M$
M
is a not necessarily compact manifold, and $H$
H
is a Tonelli Hamiltonian, we prove the set $\Sigma (U)$
Σ
(
U
)
, of points in $]0,+\infty [\times M$
]
0
,
+
∞
[
×
M
where $U$
U
is not differentiable, is locally contractible. Moreover, we study the homotopy type of $\Sigma (U)$
Σ
(
U
)
. We also give an application to the singularities of the distance function to a closed subset of a complete Riemannian manifold.