Flash flood disaster is one of the important natural disasters, bringing harm to human life and causing serious economic losses, so it is urgent to improve the accuracy of flash flood warning. To determine the critical rainfall and early warning indicators of disaster prevention objects, the Shuyuan Watershed of Qufu City Shandong Province was selected as the research object, the key disaster prevention objects were screened and finally, Hengmiao Village and Gaolou Village were selected as typical disaster prevention objects. Empirical analysis method, Storm analysis method, and model analysis method were used to calculate the critical rainfall at different times under different soil water content conditions, compare and analyze the rationality and existing problems of these three methods, and comprehensively determine the indicators of typical disaster prevention objects under different circumstances. The results show that the value of the index calculated by the storm analysis method is small and calculated by the model analysis method is large. This paper can improve the accuracy of flash flood warning, select the critical rainfall calculation method according to local conditions, accurately calculate the parameter values, and deal with the problem of effective early warning in the region as a whole.

Infiltration and anti-filtration recharge-pumping wells (hereinafter, referred to as IAF recharge-pumping wells) can enable rain-flood flowing in rivers or channel recharge to aquifers, in flood periods, and pump groundwater to be utilized in non-flood periods. In this study, a round IAF recharge-pumping well and a square IAF recharge-pumping well were developed, the structure and characteristic were introduced, the calculation equations of single-well recharge quantity of IAF recharge-pumping wells, in unconfined aquifers were deduced, and the steady-state flow recharge test was conducted in the laboratory. The conclusions were as follows. The theoretical equation of the single-well recharge quantity was reasonable. Compared to existing anti-filtration recharge wells, the new IAF recharge-pumping well had stronger anti-deposit and anti-scour abilities and the single-well recharge quantity increased by 400%. Compared to the square IAF recharge-pumping well, the round IAF recharge-pumping well had a better inlet flow pattern and a larger single-well recharge quantity. With an increase in the test times, the single-well recharge quantity gradually decreased and tended to be stable. The existence of the pumping pipe had a little influence on the single-well recharge quantity.

The mechanical properties and failure mechanism of composite geomembrane air expansion deformation occurring in plain reservoirs or artificial lakes are investigated. Composite geomembranes are formed by the heat combination of a core geomembrane and the geotextiles on two sides. The deformation is simplified as a spherical bulging deformation under ring-restrained conditions. The experiment is performed by a self-developed apparatus. Rules of the air expansion deformation and failure are summarized, and the following conclusions are drawn. Air expansion deformation and failure belong to tensile failure, which begins at the crown top, and a typical failure mode is a crack distributed along the crown (great circle). The composite geomembrane produces synergistic deformation during the air expansion process, and the outer geotextile bears a large tensile force. The geotextile and geomembrane are broken simultaneously and are not separated during the failure process. A 34-Hz frequency is selected as the basic loading rate for the air expansion tests of the composite geomembrane; at this frequency, the bursting pressure is 3.24 MPa, and the bursting height is 26.1 mm. The tensile stress and strain curve of a composite geomembrane can be divided into four stages: elastic stage, yield stage, strengthening phase, and breaking stage. The air expansion deformation degree is inhomogeneous, at which the maximum is at the crown top and the minimum is at the ring constraint. The air expansion elongation at break is 17.3 %, which is far less than the uniaxial tensile elongation at break of 51.7 %.

The geomembrane liner has been extensively utilized as a containment system for the construction of reservoirs, ponds, and lagoons. In the reservoirs that are completely lined with geomembranes, a number of factors could cause geomembrane air expansion, including the rising of groundwater level, a rapid decrease in the reservoir water level, and geomembrane defects. Geomembrane air expansion would increase the risk of failure of the geomembrane liner. At present, sand ditch exhaust systems are often employed to eliminate pore air pressure, however, the effect is not obvious. In this article, the method of vacuumizing is proposed to eliminate geomembrane air expansion. A field experiment was performed to verify the validity of the proposed method. Experimental results indicated that: (1) during the storage period of the plain reservoir, leakage water flowed into the sand ditch exhaust system, which would greatly reduce pore air exhaust efficiency of the sand ditch exhaust system; (2) the proposed method could be employed to suck out the pore air under geomembrane liner, and thus, the problem of geomembrane air expansion was solved effectively.

The construction of anti-seepage wall is an important part of the Rushan River underground reservoir project. The quality inspection of the anti-seepage wall is an important measures to ensure the anti-seepage reliability, and has important practical significance. The quality of anti-seepage wall is inspected by ultra-high density electrical method, on the basis of investigating the stratum lithology of Rushan River and the construction method of anti-seepage wall. The following conclusions are as drawn. (1) Ultra-high density electrical method greatly improves the quantity of data acquisition by using the mode of multi-channel, multiple electrode, data automatic acquisition. (2) The arrangement of disposable survey line is adopted in the inspection, which can easy to operate and save inspection time. (3) With increasing of the inspection data, the error of inversion system is reduced, and the contour map of apparent resistivity is more reliable. (4) The contour map of apparent resistivity shows that the anti-seepage wall has good continuity, and obvious discontinuous anti-seepage wall is not found; the connection between the anti-seepage wall and the bedrock is well, indicating that the quality of anti-seepage wall meets the anticipated effect, the next construction can be implemented.