Technically it is possible from the sensors resolution point of view. Unfortunately, since the ultrasonic sensors need to be close to the target for having satisfying resolution, you need an installation (fixed) frame to install them on. This is the actual problem that you have. On the other hand, the classical inclinometer tubes give you very good results over the whole section of the retaining wall or the slope with a minimum cost. The ultrasonic sensors are more expensive and the measurement is pointwise. Anyway, depending on your application you may employ laser scanning with a robotic total station, or, if you afford, interferometer scanning of the slope or structure.

Thank you Mr Serbulea for your impressive answer .But i wanna design system that has on-board micro-controller CPU for movement detection and monitoring ,I need a sensor that has digital signal output like PWM signals.since tunnel space usually is in- use for muck transport and etc,I wanna it be wireless sensor.do you have any suggestion about it?

Now I see... So, you want to measure the RELATIVE displacement of two walls in close proximity (such as the ones for tunnels), your project becomes more feasible. It is still a problem of the reference frame, but in this case the best thing, in my opinion, would be to measure the whole section all-around, with an even number of sensors (at least four: up-down and left-right) placed along the frame on opposite directions, so that the displacements of the frame may be compensated by averagind the values of the two opposite sensors and the result be compared with the previous reading. So you compare the incremental differences of the averages on the opposing pairs of sensors.

Regarding the build, this depends on your specific needs. Indeed, to have a flexible system (maybe you eant to install 6 or 8 or 10 sensors), the simplest and cheapest way is to use a system made of several units sensor + arduino board + bluetooth (or wifi) + power system connected to an Android tablet, so you can register as many units as you want. Technically, you may use class 1 or 2 bluetooth for small distances (100m or 10m, respectively) or wifi for bigger distances. If you put everyting on a wired bus, you risk jamming if a unit is blocked on transmission. Wireles you can automatically disregard the faulty ones.

Thank Mr Serbulea for complete answer.If i need help in this project,could i account on your help?

Of course, any time.