To discriminate and measure the whole stability of unlined shallow earth tunnel in theory

considering the effect of oblique slip surface beside tunnel body

a theoretical solution of ultimate surcharge is deduced by adopting the limit equilibrium method during the occurrence of the tunnel overall instability

and then the solution is examined using the typical loading tests. It is found that the solution of ultimate surcharge formulation is close to the test results. On the basis

the ratio of sliding resistance to sliding force is defined as the whole stability safety factor

and its influencing aspects are analyzed. It is shown that the stability safety factor increases along with the increment of the cohesive force and the internal friction angle

and the effect of cohesive force on the safety factor is significant

but the effect of internal friction angle is less potent. The stability safety factor decreases with the increment of the span

the depth-span ratio

and the surcharge of earth tunnel

but the surcharge has less effect on the stability safety factor when it is larger. With the increment of the height-span ratio

the stability safety factor decreases as the cohesive force is low

but it increases firstly and then decreases as the cohesive force is high. Finally

the whole stability safety factor is verified by typical loading experiments

demonstrating that the calculation error is within the engineering allowance.