Abstract: A linear moveout correction and phase-delay focusing reverse-time migration method for tunnel seismic data includes following steps: step 1: eliminating the influence of offset using a linear moveout correction method, converting single-shot tunnel seismic records into self-excited and self-received data, and converting the corresponding shot locations to new locations; step 2: during forward extrapolation and reverse-time extrapolation, assigning phase delays sequentially to a wavelet and self-excited and self-received data according to a location of seismic trace to perform reverse-time migration (RTM) imaging; and step 3: weighting and stacking the RTM imaging results using signal-to-noise ratio statistics to obtain final focusing RTM imaging results. The present disclosure aims to overcome the influences of small offsets, distinguish the types and spatial structural characteristics of unfavorable geological bodies, and improve the accuracy of RTM imaging.

Abstract: A three-dimensional reverse-time extrapolation method for seismic waves includes the following steps: picking first-arrival traveltime information of seismic data excited and received by a tunnel wall, and calculating a P-wave velocity and an S-wave velocity of a surrounding rock based on a spacing between shot points; performing three-dimensional reverse-time extrapolation from maximum time to minimum time by using the resulting P-wave velocity and the S-wave velocity as a velocity model, and deploying a virtual geophone on a tunnel face during the calculation to receive a wavefield in the three-dimensional reverse-time extrapolation; and performing autocorrelation imaging on the wavefield after the three-dimensional reverse-time extrapolation, and further converting a seismic wavefield excited by a tunnel wall and received by the tunnel face into a seismic wavefield excited and received by the tunnel face.

Abstract: The present disclosure belongs to the field of water treatment, and specifically relates to a positively charged quaternary ammonium salt polymer catalyst and its preparation method and an application thereof. The catalyst provided by the present disclosure is prepared from a positively charged quaternary ammonium salt precursor through polymerization and anion exchange, wherein the positively charged quaternary ammonium salt precursor is the reaction product of an acrylate and a haloalkane; the acrylate is selected from the group consisting of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethyl 3-(dimethylamino)acrylate and a mixture thereof; the haloalkane is selected from the group consisting of bromoundecane, bromododecane, bromotetradecane, bromohexadecane, bromoeicosane, chlorododecane, chlorotetradecane, chlorohexadecane, and a mixture thereof.